diff --git a/lib/mobilizon/events/comment.ex b/lib/mobilizon/events/comment.ex
index cbc9a6f5..adf137ba 100644
--- a/lib/mobilizon/events/comment.ex
+++ b/lib/mobilizon/events/comment.ex
@@ -40,4 +40,11 @@ defmodule Mobilizon.Events.Comment do
     |> put_change(:url, url)
     |> validate_required([:text, :actor_id, :url])
   end
+
+  @doc """
+  Returns the id of the first comment in the conversation
+  """
+  def get_thread_id(%Comment{id: id, origin_comment_id: origin_comment_id}) do
+    origin_comment_id || id
+  end
 end
diff --git a/lib/service/activity_pub/activity_pub.ex b/lib/service/activity_pub/activity_pub.ex
index 9f2a3e4a..f140d748 100644
--- a/lib/service/activity_pub/activity_pub.ex
+++ b/lib/service/activity_pub/activity_pub.ex
@@ -50,6 +50,8 @@ defmodule Mobilizon.Service.ActivityPub do
   @spec fetch_object_from_url(String.t()) :: tuple()
   def fetch_object_from_url(url) do
     with true <- String.starts_with?(url, "http"),
+         nil <- Events.get_event_by_url(url),
+         nil <- Events.get_comment_from_url(url),
          {:ok, %{body: body, status_code: code}} when code in 200..299 <-
            HTTPoison.get(
              url,
@@ -59,8 +61,6 @@ defmodule Mobilizon.Service.ActivityPub do
              recv_timeout: 20_000
            ),
          {:ok, data} <- Jason.decode(body),
-         nil <- Events.get_event_by_url(data["id"]),
-         nil <- Events.get_comment_from_url(data["id"]),
          params <- %{
            "type" => "Create",
            "to" => data["to"],
diff --git a/lib/service/activity_pub/utils.ex b/lib/service/activity_pub/utils.ex
index d52b62c4..60745349 100644
--- a/lib/service/activity_pub/utils.ex
+++ b/lib/service/activity_pub/utils.ex
@@ -14,6 +14,7 @@ defmodule Mobilizon.Service.ActivityPub.Utils do
   alias MobilizonWeb
   alias MobilizonWeb.Router.Helpers
   alias MobilizonWeb.Endpoint
+  alias Mobilizon.Service.ActivityPub
   alias Ecto.{Changeset, UUID}
   import Ecto.Query
 
@@ -137,11 +138,30 @@ defmodule Mobilizon.Service.ActivityPub.Utils do
         "text" => object_data["content"],
         "url" => object_data["id"],
         "actor_id" => actor_id,
-        "in_reply_to_comment_id" => object_data["inReplyTo"],
+        "in_reply_to_comment_id" => nil,
+        "event_id" => nil,
         # probably
         "local" => false
       }
 
+      # We fetch the parent object
+      data =
+        case ActivityPub.fetch_object_from_url(object_data["inReplyTo"]) do
+          # Reply to an event (Comment)
+          {:ok, %Event{id: id}} ->
+            data |> Map.put("event_id", id)
+
+          # Reply to a comment (Comment)
+          {:ok, %Comment{id: id} = comment} ->
+            data
+            |> Map.put("in_reply_to_comment_id", id)
+            |> Map.put("origin_comment_id", comment |> Comment.get_thread_id())
+
+          # Anthing else is kind of a MP
+          _ ->
+            data
+        end
+
       require Logger
       Logger.info("comment data ready to be inserted")
       Logger.info(inspect(data))