pundit: convert comments to pundit.

app/policies/comment_policy.rb

@@ -0,0 +1,19 @@
+class CommentPolicy < ApplicationPolicy
+  def update?
+    unbanned? && (user.is_moderator? || record.updater_id == user.id)
+  end
+
+  def can_sticky_comment?
+    user.is_moderator?
+  end
+
+  def permitted_attributes_for_create
+    [:body, :post_id, :do_not_bump_post, (:is_sticky if can_sticky_comment?)].compact
+  end
+
+  def permitted_attributes_for_update
+    [:body, :is_deleted, (:is_sticky if can_sticky_comment?)].compact
+  end
+
+  alias_method :undelete?, :update?
+end