Clarify and tweak setting up `savehist'

README.org

@@ -1355,18 +1355,16 @@ completion in any buffer.
 Listing [[lst:enable-vertico-mode]] configures and enables =savehist-mode= and
 enables =vertico-mode=.  The documentation src_emacs-lisp{(describe-function
 'savehist-mode)} why it is best to turn on =savehist-mode= in the Emacs init
-file.
+file.  BUG: Adding ~eww-history~, ~register-alist~, ~regexp-search-string~, or
+~search-string~ to ~savehist-additional-variables~ fails to save the relevant
+histories.
 
 #+caption[Enable =savehist-mode= and =vertico-mode=]:
 #+caption: Enable =savehist-mode= and =vertico-mode=.
 #+name: lst:enable-vertico-mode
 #+begin_src emacs-lisp -n :results silent
 (when (require 'savehist nil 'noerror)
-  (setopt savehist-additional-variables '(eww-history
-                                          kill-ring
-                                          regexp-search-string
-                                          search-ring
-                                          search-string))
+  (setopt savehist-additional-variables '(kill-ring search-ring))
   (savehist-mode +1))
 (when (and (ensure-package-installation 'vertico)
            (fboundp 'vertico-mode))