diff --git a/.credo.exs b/.credo.exs
index f8418d5a..de39ccce 100644
--- a/.credo.exs
+++ b/.credo.exs
@@ -21,8 +21,8 @@
         # You can give explicit globs or simply directories.
         # In the latter case `**/*.{ex,exs}` will be used.
         #
-        included: ["lib/", "src/", "test/", "web/", "apps/"],
-        excluded: [~r"/_build/", ~r"/deps/"]
+        included: ["lib/", "src/", "test/"],
+        excluded: [~r"/_build/", ~r"/deps/", ~r"/js/"]
       },
       #
       # If you create your own checks, you must specify the source files for
@@ -51,12 +51,12 @@
         #
         ## Consistency Checks
         #
-        {Credo.Check.Consistency.ExceptionNames},
-        {Credo.Check.Consistency.LineEndings},
-        {Credo.Check.Consistency.ParameterPatternMatching},
-        {Credo.Check.Consistency.SpaceAroundOperators},
-        {Credo.Check.Consistency.SpaceInParentheses},
-        {Credo.Check.Consistency.TabsOrSpaces},
+        {Credo.Check.Consistency.ExceptionNames, []},
+        {Credo.Check.Consistency.LineEndings, []},
+        {Credo.Check.Consistency.ParameterPatternMatching, []},
+        {Credo.Check.Consistency.SpaceAroundOperators, []},
+        {Credo.Check.Consistency.SpaceInParentheses, []},
+        {Credo.Check.Consistency.TabsOrSpaces, []},
 
         #
         ## Design Checks
@@ -64,92 +64,91 @@
         # You can customize the priority of any check
         # Priority values are: `low, normal, high, higher`
         #
-        {Credo.Check.Design.AliasUsage, priority: :low},
-        # For some checks, you can also set other parameters
-        #
-        # If you don't want the `setup` and `test` macro calls in ExUnit tests
-        # or the `schema` macro in Ecto schemas to trigger DuplicatedCode, just
-        # set the `excluded_macros` parameter to `[:schema, :setup, :test]`.
-        #
-        {Credo.Check.Design.DuplicatedCode, excluded_macros: []},
+        {Credo.Check.Design.AliasUsage,
+         [priority: :low, if_nested_deeper_than: 2, if_called_more_often_than: 0]},
         # You can also customize the exit_status of each check.
         # If you don't want TODO comments to cause `mix credo` to fail, just
         # set this value to 0 (zero).
         #
-        {Credo.Check.Design.TagTODO, exit_status: 0},
-        {Credo.Check.Design.TagFIXME},
+        {Credo.Check.Design.TagTODO, [exit_status: 0]},
+        {Credo.Check.Design.TagFIXME, []},
 
         #
         ## Readability Checks
         #
-        {Credo.Check.Readability.AliasOrder},
-        {Credo.Check.Readability.FunctionNames},
-        {Credo.Check.Readability.LargeNumbers},
-        {Credo.Check.Readability.MaxLineLength, priority: :low, max_length: 80},
-        {Credo.Check.Readability.ModuleAttributeNames},
-        {Credo.Check.Readability.ModuleDoc},
-        {Credo.Check.Readability.ModuleNames},
-        {Credo.Check.Readability.ParenthesesOnZeroArityDefs},
-        {Credo.Check.Readability.ParenthesesInCondition},
-        {Credo.Check.Readability.PredicateFunctionNames},
-        {Credo.Check.Readability.PreferImplicitTry},
-        {Credo.Check.Readability.RedundantBlankLines},
-        {Credo.Check.Readability.StringSigils},
-        {Credo.Check.Readability.TrailingBlankLine},
-        {Credo.Check.Readability.TrailingWhiteSpace},
-        {Credo.Check.Readability.VariableNames},
-        {Credo.Check.Readability.Semicolons},
-        {Credo.Check.Readability.SpaceAfterCommas},
+        {Credo.Check.Readability.AliasOrder, []},
+        {Credo.Check.Readability.FunctionNames, []},
+        {Credo.Check.Readability.LargeNumbers, []},
+        {Credo.Check.Readability.MaxLineLength, [priority: :low, max_length: 120]},
+        {Credo.Check.Readability.ModuleAttributeNames, []},
+        {Credo.Check.Readability.ModuleDoc, []},
+        {Credo.Check.Readability.ModuleNames, []},
+        {Credo.Check.Readability.ParenthesesInCondition, []},
+        {Credo.Check.Readability.ParenthesesOnZeroArityDefs, []},
+        {Credo.Check.Readability.PredicateFunctionNames, []},
+        {Credo.Check.Readability.PreferImplicitTry, []},
+        {Credo.Check.Readability.RedundantBlankLines, []},
+        {Credo.Check.Readability.Semicolons, []},
+        {Credo.Check.Readability.SpaceAfterCommas, []},
+        {Credo.Check.Readability.StringSigils, []},
+        {Credo.Check.Readability.TrailingBlankLine, []},
+        {Credo.Check.Readability.TrailingWhiteSpace, []},
+        {Credo.Check.Readability.VariableNames, []},
 
         #
         ## Refactoring Opportunities
         #
-        {Credo.Check.Refactor.DoubleBooleanNegation},
-        {Credo.Check.Refactor.CondStatements},
-        {Credo.Check.Refactor.CyclomaticComplexity},
-        {Credo.Check.Refactor.FunctionArity},
-        {Credo.Check.Refactor.LongQuoteBlocks},
-        {Credo.Check.Refactor.MatchInCondition},
-        {Credo.Check.Refactor.NegatedConditionsInUnless},
-        {Credo.Check.Refactor.NegatedConditionsWithElse},
-        {Credo.Check.Refactor.Nesting, max_nesting: 3},
+        {Credo.Check.Refactor.CondStatements, []},
+        {Credo.Check.Refactor.CyclomaticComplexity, []},
+        {Credo.Check.Refactor.FunctionArity, []},
+        {Credo.Check.Refactor.LongQuoteBlocks, []},
+        {Credo.Check.Refactor.MapInto, []},
+        {Credo.Check.Refactor.MatchInCondition, []},
+        {Credo.Check.Refactor.NegatedConditionsInUnless, []},
+        {Credo.Check.Refactor.NegatedConditionsWithElse, []},
+        {Credo.Check.Refactor.Nesting, [
+          max_nesting: 3
+        ]},
         {Credo.Check.Refactor.PipeChainStart,
-         excluded_argument_types: [:atom, :binary, :fn, :keyword], excluded_functions: []},
-        {Credo.Check.Refactor.UnlessWithElse},
+         [
+           excluded_argument_types: [:atom, :binary, :fn, :keyword, :number],
+           excluded_functions: [],
+           exit_status: 0
+         ]},
+        {Credo.Check.Refactor.UnlessWithElse, []},
 
         #
         ## Warnings
         #
-        {Credo.Check.Warning.BoolOperationOnSameValues},
-        {Credo.Check.Warning.ExpensiveEmptyEnumCheck},
-        {Credo.Check.Warning.IExPry},
-        {Credo.Check.Warning.IoInspect},
-        {Credo.Check.Warning.LazyLogging},
-        {Credo.Check.Warning.OperationOnSameValues},
-        {Credo.Check.Warning.OperationWithConstantResult},
-        {Credo.Check.Warning.UnusedEnumOperation},
-        {Credo.Check.Warning.UnusedFileOperation},
-        {Credo.Check.Warning.UnusedKeywordOperation},
-        {Credo.Check.Warning.UnusedListOperation},
-        {Credo.Check.Warning.UnusedPathOperation},
-        {Credo.Check.Warning.UnusedRegexOperation},
-        {Credo.Check.Warning.UnusedStringOperation},
-        {Credo.Check.Warning.UnusedTupleOperation},
-        {Credo.Check.Warning.RaiseInsideRescue},
+        {Credo.Check.Warning.BoolOperationOnSameValues, []},
+        {Credo.Check.Warning.ExpensiveEmptyEnumCheck, []},
+        {Credo.Check.Warning.IExPry, []},
+        {Credo.Check.Warning.IoInspect, []},
+        {Credo.Check.Warning.LazyLogging, []},
+        {Credo.Check.Warning.OperationOnSameValues, []},
+        {Credo.Check.Warning.OperationWithConstantResult, []},
+        {Credo.Check.Warning.RaiseInsideRescue, []},
+        {Credo.Check.Warning.UnusedEnumOperation, []},
+        {Credo.Check.Warning.UnusedFileOperation, []},
+        {Credo.Check.Warning.UnusedKeywordOperation, []},
+        {Credo.Check.Warning.UnusedListOperation, []},
+        {Credo.Check.Warning.UnusedPathOperation, []},
+        {Credo.Check.Warning.UnusedRegexOperation, []},
+        {Credo.Check.Warning.UnusedStringOperation, []},
+        {Credo.Check.Warning.UnusedTupleOperation, []},
 
         #
         # Controversial and experimental checks (opt-in, just remove `, false`)
         #
+        {Credo.Check.Consistency.MultiAliasImportRequireUse, false},
+        {Credo.Check.Design.DuplicatedCode, false},
+        {Credo.Check.Readability.Specs, false},
         {Credo.Check.Refactor.ABCSize, false},
         {Credo.Check.Refactor.AppendSingleItem, false},
+        {Credo.Check.Refactor.DoubleBooleanNegation, false},
         {Credo.Check.Refactor.VariableRebinding, false},
         {Credo.Check.Warning.MapGetUnsafePass, false},
-        {Credo.Check.Consistency.MultiAliasImportRequireUse, false},
-
-        #
-        # Deprecated checks (these will be deleted after a grace period)
-        #
-        {Credo.Check.Readability.Specs, false}
+        {Credo.Check.Warning.UnsafeToAtom, false}
 
         #
         # Custom checks can be created using `mix credo.gen.check`.
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b7033ac9..802952f4 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -36,12 +36,13 @@ js:
     untracked: false
     expire_in: 30 days
 
-elixir_format:
+elixir_check:
   stage: back
   before_script:
     - mix deps.get
   script:
     - mix format --check-formatted --dry-run
+    - mix credo list
   cache:
     paths:
       - deps
diff --git a/lib/mix/tasks/mobilizon/instance.ex b/lib/mix/tasks/mobilizon/instance.ex
index 0f6c5d87..99c18388 100644
--- a/lib/mix/tasks/mobilizon/instance.ex
+++ b/lib/mix/tasks/mobilizon/instance.ex
@@ -63,7 +63,7 @@ defmodule Mix.Tasks.Mobilizon.Instance do
     will_overwrite = Enum.filter(paths, &File.exists?/1)
     proceed? = Enum.empty?(will_overwrite) or Keyword.get(options, :force, false)
 
-    unless not proceed? do
+    if proceed? do
       [domain, port | _] =
         String.split(
           Common.get_option(
@@ -163,7 +163,7 @@ defmodule Mix.Tasks.Mobilizon.Instance do
     else
       Mix.shell().error(
         "The task would have overwritten the following files:\n" <>
-          (Enum.map(will_overwrite, &"- #{&1}\n") |> Enum.join("")) <>
+          (will_overwrite |> Enum.map(&"- #{&1}\n") |> Enum.join("")) <>
           "Rerun with `-f/--force` to overwrite them."
       )
     end
diff --git a/lib/mobilizon/actors/actors.ex b/lib/mobilizon/actors/actors.ex
index c599e982..dbc37865 100644
--- a/lib/mobilizon/actors/actors.ex
+++ b/lib/mobilizon/actors/actors.ex
@@ -68,7 +68,7 @@ defmodule Mobilizon.Actors do
              where: u.id == ^user.id
            )
          ) do
-      nil -> get_actors_for_user(user) |> hd
+      nil -> user |> get_actors_for_user() |> hd
       actor -> actor
     end
   end
diff --git a/lib/mobilizon/actors/service/tools.ex b/lib/mobilizon/actors/service/tools.ex
index 4c6e9aef..39ff2a0f 100644
--- a/lib/mobilizon/actors/service/tools.ex
+++ b/lib/mobilizon/actors/service/tools.ex
@@ -1,4 +1,7 @@
 defmodule Mobilizon.Actors.Service.Tools do
+  @moduledoc """
+  Common functions for actors services
+  """
   alias Mobilizon.Actors.User
 
   @spec we_can_send_email(User.t(), atom()) :: :ok | {:error, :email_too_soon}
diff --git a/lib/mobilizon_web/api/comments.ex b/lib/mobilizon_web/api/comments.ex
index c1e3d40a..f05d4547 100644
--- a/lib/mobilizon_web/api/comments.ex
+++ b/lib/mobilizon_web/api/comments.ex
@@ -17,13 +17,18 @@ defmodule MobilizonWeb.API.Comments do
   Creates a comment from an actor and a status
   """
   @spec create_comment(String.t(), String.t(), String.t()) :: {:ok, Activity.t()} | any()
-  def create_comment(from_username, status, visibility \\ "public", inReplyToCommentURL \\ nil) do
+  def create_comment(
+        from_username,
+        status,
+        visibility \\ "public",
+        in_reply_to_comment_URL \\ nil
+      ) do
     with {:local_actor, %Actor{url: url} = actor} <-
            {:local_actor, Actors.get_local_actor_by_name(from_username)},
          status <- String.trim(status),
          mentions <- Formatter.parse_mentions(status),
-         inReplyToComment <- get_in_reply_to_comment(inReplyToCommentURL),
-         {to, cc} <- to_for_actor_and_mentions(actor, mentions, inReplyToComment, visibility),
+         in_reply_to_comment <- get_in_reply_to_comment(in_reply_to_comment_URL),
+         {to, cc} <- to_for_actor_and_mentions(actor, mentions, in_reply_to_comment, visibility),
          tags <- Formatter.parse_tags(status),
          content_html <-
            make_content_html(
@@ -37,7 +42,7 @@ defmodule MobilizonWeb.API.Comments do
              url,
              to,
              content_html,
-             inReplyToComment,
+             in_reply_to_comment,
              tags,
              cc
            ) do
diff --git a/lib/mobilizon_web/context.ex b/lib/mobilizon_web/context.ex
index 04884dc5..9f88807d 100644
--- a/lib/mobilizon_web/context.ex
+++ b/lib/mobilizon_web/context.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Context do
+  @moduledoc """
+  Guardian context for MobilizonWeb
+  """
   @behaviour Plug
 
   import Plug.Conn
diff --git a/lib/mobilizon_web/controllers/activity_pub_controller.ex b/lib/mobilizon_web/controllers/activity_pub_controller.ex
index 10db79ac..0777f851 100644
--- a/lib/mobilizon_web/controllers/activity_pub_controller.ex
+++ b/lib/mobilizon_web/controllers/activity_pub_controller.ex
@@ -23,14 +23,12 @@ defmodule MobilizonWeb.ActivityPubController do
 
   def actor(conn, %{"name" => name}) do
     with %Actor{} = actor <- Actors.get_local_actor_by_name(name) do
-      cond do
-        conn |> get_req_header("accept") |> is_ap_header() ->
-          conn |> render_ap_actor(actor)
-
-        true ->
-          conn
-          |> put_resp_content_type("text/html")
-          |> send_file(200, "priv/static/index.html")
+      if conn |> get_req_header("accept") |> is_ap_header() do
+        conn |> render_ap_actor(actor)
+      else
+        conn
+        |> put_resp_content_type("text/html")
+        |> send_file(200, "priv/static/index.html")
       end
     else
       nil -> {:error, :not_found}
diff --git a/lib/mobilizon_web/resolvers/category.ex b/lib/mobilizon_web/resolvers/category.ex
index 514b8c53..d7d8997e 100644
--- a/lib/mobilizon_web/resolvers/category.ex
+++ b/lib/mobilizon_web/resolvers/category.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Resolvers.Category do
+  @moduledoc """
+  Handles the category-related GraphQL calls
+  """
   require Logger
   alias Mobilizon.Actors.User
 
diff --git a/lib/mobilizon_web/resolvers/comment.ex b/lib/mobilizon_web/resolvers/comment.ex
index be02e0ab..2fd74008 100644
--- a/lib/mobilizon_web/resolvers/comment.ex
+++ b/lib/mobilizon_web/resolvers/comment.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Resolvers.Comment do
+  @moduledoc """
+  Handles the comment-related GraphQL calls
+  """
   require Logger
   alias Mobilizon.Events.Comment
   alias Mobilizon.Activity
diff --git a/lib/mobilizon_web/resolvers/event.ex b/lib/mobilizon_web/resolvers/event.ex
index 3cdff854..f75ea692 100644
--- a/lib/mobilizon_web/resolvers/event.ex
+++ b/lib/mobilizon_web/resolvers/event.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Resolvers.Event do
+  @moduledoc """
+  Handles the event-related GraphQL calls
+  """
   alias Mobilizon.Service.ActivityPub
   alias Mobilizon.Activity
   alias Mobilizon.Actors
diff --git a/lib/mobilizon_web/resolvers/group.ex b/lib/mobilizon_web/resolvers/group.ex
index 542fb0fe..fc73fd5a 100644
--- a/lib/mobilizon_web/resolvers/group.ex
+++ b/lib/mobilizon_web/resolvers/group.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Resolvers.Group do
+  @moduledoc """
+  Handles the group-related GraphQL calls
+  """
   alias Mobilizon.Actors
   alias Mobilizon.Actors.{Actor}
   alias Mobilizon.Service.ActivityPub
diff --git a/lib/mobilizon_web/resolvers/person.ex b/lib/mobilizon_web/resolvers/person.ex
index d478f972..4163e2b8 100644
--- a/lib/mobilizon_web/resolvers/person.ex
+++ b/lib/mobilizon_web/resolvers/person.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Resolvers.Person do
+  @moduledoc """
+  Handles the person-related GraphQL calls
+  """
   alias Mobilizon.Actors
   alias Mobilizon.Service.ActivityPub
 
diff --git a/lib/mobilizon_web/resolvers/upload.ex b/lib/mobilizon_web/resolvers/upload.ex
deleted file mode 100644
index 8d50226a..00000000
--- a/lib/mobilizon_web/resolvers/upload.ex
+++ /dev/null
@@ -1,2 +0,0 @@
-defmodule MobilizonWeb.Resolvers.Upload do
-end
diff --git a/lib/mobilizon_web/resolvers/user.ex b/lib/mobilizon_web/resolvers/user.ex
index 236cec39..37566872 100644
--- a/lib/mobilizon_web/resolvers/user.ex
+++ b/lib/mobilizon_web/resolvers/user.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Resolvers.User do
+  @moduledoc """
+  Handles the user-related GraphQL calls
+  """
   alias Mobilizon.Actors.{User, Actor}
   alias Mobilizon.Actors
   require Logger
diff --git a/lib/mobilizon_web/schema.ex b/lib/mobilizon_web/schema.ex
index 35a9c149..02e7543a 100644
--- a/lib/mobilizon_web/schema.ex
+++ b/lib/mobilizon_web/schema.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Schema do
+  @moduledoc """
+  GraphQL schema representation
+  """
   use Absinthe.Schema
 
   import Absinthe.Resolution.Helpers, only: [dataloader: 1]
diff --git a/lib/mobilizon_web/upload_plug.ex b/lib/mobilizon_web/upload_plug.ex
index e22fe440..93c14241 100644
--- a/lib/mobilizon_web/upload_plug.ex
+++ b/lib/mobilizon_web/upload_plug.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.UploadPlug do
+  @moduledoc """
+  Plug to intercept uploads
+  """
   use Plug.Builder
 
   plug(Plug.Static,
diff --git a/lib/mobilizon_web/uploaders/avatar.ex b/lib/mobilizon_web/uploaders/avatar.ex
index 8583122d..cf81766d 100644
--- a/lib/mobilizon_web/uploaders/avatar.ex
+++ b/lib/mobilizon_web/uploaders/avatar.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Uploaders.Avatar do
+  @moduledoc """
+  Handles avatar uploads
+  """
   use Arc.Definition
 
   # Include ecto support (requires package arc_ecto installed):
diff --git a/lib/mobilizon_web/uploaders/category.ex b/lib/mobilizon_web/uploaders/category.ex
index a42c41ac..247085f4 100644
--- a/lib/mobilizon_web/uploaders/category.ex
+++ b/lib/mobilizon_web/uploaders/category.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.Uploaders.Category do
+  @moduledoc """
+  Handles file uploads for categories
+  """
   use Arc.Definition
   use Arc.Ecto.Definition
 
diff --git a/lib/service/activity_pub/activity_pub.ex b/lib/service/activity_pub/activity_pub.ex
index c3bc3c80..1fc8fbcb 100644
--- a/lib/service/activity_pub/activity_pub.ex
+++ b/lib/service/activity_pub/activity_pub.ex
@@ -43,14 +43,7 @@ defmodule Mobilizon.Service.ActivityPub do
   def insert(map, local \\ true) when is_map(map) do
     with map <- lazy_put_activity_defaults(map),
          :ok <- insert_full_object(map) do
-      object_id =
-        cond do
-          is_map(map["object"]) ->
-            map["object"]["id"]
-
-          is_binary(map["object"]) ->
-            map["id"]
-        end
+      object_id = if is_map(map["object"]), do: map["object"]["id"], else: map["id"]
 
       map = if local, do: Map.put(map, "id", "#{object_id}/activity"), else: map
 
@@ -384,7 +377,7 @@ defmodule Mobilizon.Service.ActivityPub do
 
     {:ok, data} = Transmogrifier.prepare_outgoing(activity.data)
     json = Jason.encode!(data)
-    Logger.debug("Remote inboxes are : #{inspect(remote_inboxes)}")
+    Logger.debug(fn -> "Remote inboxes are : #{inspect(remote_inboxes)}" end)
 
     Enum.each(remote_inboxes, fn inbox ->
       Federator.enqueue(:publish_single_ap, %{
diff --git a/lib/service/activity_pub/transmogrifier.ex b/lib/service/activity_pub/transmogrifier.ex
index 9e8a13ac..96544634 100644
--- a/lib/service/activity_pub/transmogrifier.ex
+++ b/lib/service/activity_pub/transmogrifier.ex
@@ -48,28 +48,35 @@ defmodule Mobilizon.Service.ActivityPub.Transmogrifier do
     |> fix_tag
   end
 
+  def fix_in_reply_to(%{"inReplyTo" => in_reply_to} = object)
+      when not is_nil(in_reply_to) and is_bitstring(in_reply_to) do
+    in_reply_to |> do_fix_in_reply_to(object)
+  end
+
+  def fix_in_reply_to(%{"inReplyTo" => in_reply_to} = object)
+      when not is_nil(in_reply_to) and is_map(in_reply_to) do
+    if is_bitstring(in_reply_to["id"]) do
+      in_reply_to["id"] |> do_fix_in_reply_to(object)
+    end
+  end
+
+  def fix_in_reply_to(%{"inReplyTo" => in_reply_to} = object)
+      when not is_nil(in_reply_to) and is_list(in_reply_to) do
+    if is_bitstring(Enum.at(in_reply_to, 0)) do
+      in_reply_to |> Enum.at(0) |> do_fix_in_reply_to(object)
+    end
+  end
+
   def fix_in_reply_to(%{"inReplyTo" => in_reply_to} = object)
       when not is_nil(in_reply_to) do
-    in_reply_to_id =
-      cond do
-        # If the inReplyTo is just an AP ID
-        is_bitstring(in_reply_to) ->
-          in_reply_to
+    Logger.error("inReplyTo ID seem incorrect")
+    Logger.error(inspect(in_reply_to))
+    do_fix_in_reply_to("", object)
+  end
 
-        # If the inReplyTo is a object itself
-        is_map(in_reply_to) && is_bitstring(in_reply_to["id"]) ->
-          in_reply_to["id"]
-
-        # If the inReplyTo is an array
-        is_list(in_reply_to) && is_bitstring(Enum.at(in_reply_to, 0)) ->
-          Enum.at(in_reply_to, 0)
-
-        true ->
-          Logger.error("inReplyTo ID seem incorrect")
-          Logger.error(inspect(in_reply_to))
-          ""
-      end
+  def fix_in_reply_to(object), do: object
 
+  def do_fix_in_reply_to(in_reply_to_id, object) do
     case fetch_obj_helper(in_reply_to_id) do
       {:ok, replied_object} ->
         object
@@ -85,8 +92,6 @@ defmodule Mobilizon.Service.ActivityPub.Transmogrifier do
     end
   end
 
-  def fix_in_reply_to(object), do: object
-
   def fix_attachments(object) do
     attachments =
       (object["attachment"] || [])
@@ -500,7 +505,7 @@ defmodule Mobilizon.Service.ActivityPub.Transmogrifier do
 
   @spec normalize(String.t()) :: struct() | nil
   def get_anything_by_url(url) do
-    Logger.debug("Getting anything from url #{url}")
+    Logger.debug(fn -> "Getting anything from url #{url}" end)
     get_actor_url(url) || get_event_url(url) || get_comment_url(url)
   end
 
diff --git a/lib/service/activity_pub/utils.ex b/lib/service/activity_pub/utils.ex
index 2b766d6e..84e8ee56 100644
--- a/lib/service/activity_pub/utils.ex
+++ b/lib/service/activity_pub/utils.ex
@@ -171,7 +171,7 @@ defmodule Mobilizon.Service.ActivityPub.Utils do
       data =
         if Map.has_key?(object_data, "inReplyTo") && object_data["inReplyTo"] != nil &&
              object_data["inReplyTo"] != "" do
-          Logger.debug("Object has inReplyTo #{object_data["inReplyTo"]}")
+          Logger.debug(fn -> "Object has inReplyTo #{object_data["inReplyTo"]}" end)
 
           case ActivityPub.fetch_object_from_url(object_data["inReplyTo"]) do
             # Reply to an event (Comment)
diff --git a/lib/service/formatter/formatter.ex b/lib/service/formatter/formatter.ex
index 70512b0b..cae79aeb 100644
--- a/lib/service/formatter/formatter.ex
+++ b/lib/service/formatter/formatter.ex
@@ -4,6 +4,9 @@
 # Upstream: https://git.pleroma.social/pleroma/pleroma/blob/develop/lib/pleroma/formatter.ex
 
 defmodule Mobilizon.Service.Formatter do
+  @moduledoc """
+  Formats input text to structured data, extracts mentions and hashtags
+  """
   alias Mobilizon.Actors.Actor
   alias Mobilizon.Actors
 
diff --git a/mix.exs b/mix.exs
index 30476dbb..6c020b72 100644
--- a/mix.exs
+++ b/mix.exs
@@ -96,7 +96,8 @@ defmodule Mobilizon.Mixfile do
       {:mix_test_watch, "~> 0.5", only: :dev, runtime: false},
       {:ex_unit_notifier, "~> 0.1", only: :test},
       {:dialyxir, "~> 1.0.0-rc.4", only: [:dev], runtime: false},
-      {:exvcr, "~> 0.10", only: :test}
+      {:exvcr, "~> 0.10", only: :test},
+      {:credo, "~> 1.0.0", only: [:dev, :test], runtime: false}
     ]
   end
 
diff --git a/mix.lock b/mix.lock
index ed5fb9a4..9cb404dc 100644
--- a/mix.lock
+++ b/mix.lock
@@ -17,7 +17,7 @@
   "cors_plug": {:hex, :cors_plug, "1.5.2", "72df63c87e4f94112f458ce9d25800900cc88608c1078f0e4faddf20933eda6e", [:mix], [{:plug, "~> 1.3 or ~> 1.4 or ~> 1.5", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "cowboy": {:hex, :cowboy, "1.1.2", "61ac29ea970389a88eca5a65601460162d370a70018afe6f949a29dca91f3bb0", [:rebar3], [{:cowlib, "~> 1.0.2", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "~> 1.3.2", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm"},
   "cowlib": {:hex, :cowlib, "1.0.2", "9d769a1d062c9c3ac753096f868ca121e2730b9a377de23dec0f7e08b1df84ee", [:make], [], "hexpm"},
-  "credo": {:hex, :credo, "0.9.3", "76fa3e9e497ab282e0cf64b98a624aa11da702854c52c82db1bf24e54ab7c97a", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:poison, ">= 0.0.0", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
+  "credo": {:hex, :credo, "1.0.0", "aaa40fdd0543a0cf8080e8c5949d8c25f0a24e4fc8c1d83d06c388f5e5e0ea42", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm"},
   "dataloader": {:hex, :dataloader, "1.0.4", "7c2345c53c9e5b61420013fc53c8463ba347a938b61f66677eb47d9c4a53ac5d", [:mix], [{:ecto, ">= 0.0.0", [hex: :ecto, repo: "hexpm", optional: true]}], "hexpm"},
   "db_connection": {:hex, :db_connection, "1.1.3", "89b30ca1ef0a3b469b1c779579590688561d586694a3ce8792985d4d7e575a61", [:mix], [{:connection, "~> 1.0.2", [hex: :connection, repo: "hexpm", optional: false]}, {:poolboy, "~> 1.5", [hex: :poolboy, repo: "hexpm", optional: true]}, {:sbroker, "~> 1.0", [hex: :sbroker, repo: "hexpm", optional: true]}], "hexpm"},
   "decimal": {:hex, :decimal, "1.6.0", "bfd84d90ff966e1f5d4370bdd3943432d8f65f07d3bab48001aebd7030590dcc", [:mix], [], "hexpm"},
diff --git a/test/mobilizon/actors/actors_test.exs b/test/mobilizon/actors/actors_test.exs
index c88708cc..e921192f 100644
--- a/test/mobilizon/actors/actors_test.exs
+++ b/test/mobilizon/actors/actors_test.exs
@@ -228,7 +228,7 @@ defmodule Mobilizon.ActorsTest do
     @remote_actor_key {:ok,
                        {:RSAPublicKey,
                         20_890_513_599_005_517_665_557_846_902_571_022_168_782_075_040_010_449_365_706_450_877_170_130_373_892_202_874_869_873_999_284_399_697_282_332_064_948_148_602_583_340_776_692_090_472_558_740_998_357_203_838_580_321_412_679_020_304_645_826_371_196_718_081_108_049_114_160_630_664_514_340_729_769_453_281_682_773_898_619_827_376_232_969_899_348_462_205_389_310_883_299_183_817_817_999_273_916_446_620_095_414_233_374_619_948_098_516_821_650_069_821_783_810_210_582_035_456_563_335_930_330_252_551_528_035_801_173_640_288_329_718_719_895_926_309_416_142_129_926_226_047_930_429_802_084_560_488_897_717_417_403_272_782_469_039_131_379_953_278_833_320_195_233_761_955_815_307_522_871_787_339_192_744_439_894_317_730_207_141_881_699_363_391_788_150_650_217_284_777_541_358_381_165_360_697_136_307_663_640_904_621_178_632_289_787,
-                        65537}}
+                        65_537}}
     test "test get_public_key_for_url/1 with remote actor" do
       use_cassette "actors/remote_actor_mastodon_tcit" do
         assert Actor.get_public_key_for_url(@remote_account_url) == @remote_actor_key
diff --git a/test/support/abinthe_helpers.ex b/test/support/abinthe_helpers.ex
index 396b86b9..ce7e673b 100644
--- a/test/support/abinthe_helpers.ex
+++ b/test/support/abinthe_helpers.ex
@@ -1,4 +1,7 @@
 defmodule MobilizonWeb.AbsintheHelpers do
+  @moduledoc """
+  Absinthe helpers for tests
+  """
   def query_skeleton(query, query_name) do
     %{
       "operationName" => "#{query_name}",