It's easy to miss new comments when following topic subscription notifications.
Sometimes you'll follow a link from your notifications that says there are 3 new comments, and you'll see only 2 highlights (because one of the comments was moved or reverted or something) and be confused. Worse, sometimes you'll follow a link that says 15 and you only see 14 and don't even notice the comment missing the highlight.
We should at least show a message when this happens, to encourage the user to checks the diffs or history.
In the future perhaps could generate more permanent links in notifications, or help the users find where the comments went after following the links we currently use.