Re-apply eleddy's 'Revert modification date since this is fixed in

p.a.caching now.' as her commit was lost later on due to some git magic.

CHANGES.txt

@@ -4,6 +4,10 @@ Changelog
 2.2.1 (unreleased)
 ------------------
 
+- Re-apply eleddy's "Revert modification date since this is fixed in
+  p.a.caching now." as her commit was lost later on due to some git magic.
+  [thet]
+
 - Remove submitting the controlpanel form again after removing disabled tags
   fixes #13037 and #12357
   [maartenkling]

plone/app/discussion/comment.py

@@ -217,14 +217,9 @@ def notify_content_object(obj, event):
     """Tell the content object when a comment is added
     """
     content_obj = aq_parent(aq_parent(obj))
-    # set the modified date and reindex the item accordingly
-    # so that 304s work correctly. This means that adding a comment
-    # effectively counts as modifying the content type.
-    content_obj.setModificationDate(datetime.now())
     content_obj.reindexObject(idxs=('total_comments',
                                     'last_comment_date',
-                                    'commentators',
-    ))
+                                    'commentators'))
 
 
 def notify_content_object_deleted(obj, event):