I've not seen a forum do this before, though I'm sure it must exist as it seems pretty obvious.
What I think this forum could benefit the most from (aside from the normal death to trolls all forums everywhere need) is a filtering feature.
By filtering, I mean that the threads are sorted by topic. The best example would be all these Death Penalty threads could be sorted into a single topic and ignored instead of randomly cluttering the front page. It would be like creating a subfolder that you could expand or collapse with the most active or most popular thread of the topic as the main title for the that section.
Expanded it would look somewhat like this: (thread names were picked at random)
^ A Death Penalty Everyone Can Agree On! (1,2,3...Last Page)
----- ***What Kind of Death Penalty Do You Want?*** (1,2,3...Last Page)
----- Anyone else against the Death Penalty? (1,2,3)
But collapsed, it would only show the top thread.
May be too much work to implement or maintain at this juncture, but it seems to me that it could resolve issues where threads are merged due to similar content and it confuses the whole. Most importantly it would get rid of all the useless posts on the same topic for those that don't want to read them and lets people spam as many as they want since we can just not view them by collapsing the topic.