Anti-Necro Threads
 

Synopsis: If a thread is more than X days old, a reply doesn't bump it.

Long Explanation for Why We Need This:

There's already a popular mod that prevents posts to threads older than x days.
That's a nice try, but it misses the real problem. This actually fixes the problem. This is a real (better) solution.

Why?
Because some replies are very relevant. Here's an example. You have a question while in a forum. You google and use 'forum search', to find twenty old threads. None of them have a good answer. Later on, you find a good answer, add it to one thread, and then add a link to that from 19 other threads. Good job, but administration hates you and calls you a Necro... and a lot of other nasty names.

I.e. people need to post on old threads, but old threads don't need to be 'bumped'. A better mod could fix that, allowing people to post without being called a lot of nasty names.

Simple idea, good enough to win MOTM if you ask me.