New comment count is wrong after marking a reply as read in an old thread
Just noticed this when someone replied to me in a very old thread today (old enough that my
topic_visits record had been deleted). I marked the reply read from the notification page, which ended up inserting a new
topic_visit row with
num_comments as one, so the thread then showed up something like "54 comments (53 new)". This is wrong, and should actually be showing as no new comments.