If there was a irc.ycombinator.com with real-time chat topics, it might help separate "the wheat from the chaff," so to speak.
E.G. #japan-nuclear-chat
If not a chat, I'd say focus on something that doesn't fight the size of the community. Personally, I'd prefer if HN was shrunk to like '08 levels, but that's not going to happen. I think adding a service that allows for water cooler talk but keeps it isolated from deep technical discussions would work better than karmic tinkering at this point.