Hey here's a random idea.
How about whenever someone edits their post, particularly and specifically the last post on a certain thread, it updates the thread. Make sense? Here it is in more detail:
Say I make a small post. Then no one else posts after me for a while and then the topic gets "old" and has a less chance of being viewed/getting posts. Then I want to post something else a bit more interesting than my small post on the same topic. Like say, I want to write a large review of Meerkats, compared to my small post being "Haw haw haw, that's funny
". Seeing as I don't want to double post, I obviously edit my post (may be different for some PEELple, but that's what I would mostly do) and add the review. When I finish writing and save my changes, it'll be classified as a "new" post as it is bigger than the small one I made, and will update the topic, sending it to the top of the list, giving it a larger chance of people looking at it and making posts.
I don't know if that makes much sense, but if it does, I reckon it would be a good idea. Just throwing it out there. This is a Wish Void, after all.