Most of the threads on the discussion board seem to be newbie speculation threads. How about creating a speculation board, and all those mega-reply spamming threads could be moved onto that. This may provide room for some decent discussions about Bitcoin.
Part of it is that Bounty signature campaigns require a certain number of posts in the altcoin discussion thread. Creating a separate board really won't help unless you convince campaign managers to allow posting there.
In order to move the speculation threads over you would need to hand moderate it. I could write something which moves things with certain keywords and ngrams but though wouldn't be perfect. We could use a script to 'flag' certain threads which a moderator could review but a cat and mouse game would ensue.