I feel that this is a function of the size of the community plus the type of people in that community. As it gets larger, it gets filled with more of the type

I feel that this is a function of the size of the community plus the type of people in that community. As it gets larger, it gets filled with more of the type you don't want. Compare the Joel on Software discussion forum with the Business of Software discussion forum. Same site. Same format. Completely different quality of discussion. We've done experiments to help raise the quality of discussion by limiting the number of posts, having active moderators, deleting rude and obnoxious posts... But I expect asking your community to shape up doesn't work too well. The comment about PG forking the discussion probably seems like the only solution. Start over every couple of months or years.