Fix duplicate ThreadFollowers

Author: MoshiKoi

app/controllers/comments_controller.rb

@@ -227,8 +227,7 @@ def thread_unrestrict
       end
       @comment_thread.update(deleted: false, deleted_by: nil)
     when 'follow'
-      tf = ThreadFollower.find_by(comment_thread: @comment_thread, user: current_user)
-      tf&.destroy
+      ThreadFollower.where(comment_thread: @comment_thread, user: current_user).destroy_all
     else
       return not_found
     end

app/models/comment_thread.rb

@@ -13,8 +13,6 @@ class CommentThread < ApplicationRecord
   scope :publicly_available, -> { where(deleted: false).where('reply_count > 0') }
   scope :archived, -> { where(archived: true) }
 
-  after_create :create_follower
-
   def read_only?
     locked? || archived? || deleted?
   end
@@ -38,12 +36,4 @@ def self.post_followed?(post, user)
 
   private
 
-  # Comment author and post author are automatically followed to the thread. Question author is NOT
-  # automatically followed on new answer comment threads. Comment author follower creation is done
-  # on the Comment model.
-  def create_follower
-    if post.user.preference('auto_follow_comment_threads') == 'true'
-      ThreadFollower.create comment_thread: self, user: post.user
-    end
-  end
 end