If the user talk edit or mention coincides with exactly one new comment:
* Change the primary link to be a direct link to the comment
* Add a text snippet to notifications that don't already include one
(user talk edits that are not new sections).
This is done for all such notifications, regardless of whether anyone
has topic subscriptions enabled.
Bug: T281590
Bug: T253082
Change-Id: I98fbca8e57845cd7c82ad533c393db953e4e5643