If someone comes along and adds an answer or comment to a question from farther back, that question will come to the top of your list so you can notice more easily that there's been additional stuff added to it.
Chances are the system just hasn't caught up. Sometimes, I imagine the mods take a closer look at to make sure everything listed in your comment is completely appropriate for the site. This is just what I think and may not be entirely correct. Hope it helps though. : )