A few things:
1. I have noticed a rise in a sort of pseudo-badassness, wherein people who are very good at Dominion leave a comment that's undoubtedly insightful, but short, cryptic, and flippant. I really dislike this, I find it both rude and unhelpful to the game. One nice thing about the new card reveals is that there's less of this (presumably since no one knows the cards that well). (OK OK, I just upvoted a comment in the Talisman thread saying "Talisman sucks" but I mean come on, it's Talisman.)
2. I don't think Scout jokes are funny, but I doubt that's keeping people away from the forums. Same with Mine/Mint, moat, etc. In fact is it even true that we have a retention problem? Lots of new faces around here.
3. Generally when you're posting an edge-case, you don't feel like it's an edge-case, even when most people would disagree with you; I would not like to see that banned from even a proposed "serious" forum (an idea which I am not that into). There's also extreme edge-cases listed as more or less jokes; that can be a little annoying, but sometimes funny and in any event very skippable.