Ask HN: Would bitcoin tech be feasible for decentralised forum?

That doesn't make sense, bitcoins relies on insufficient processing power with cryptography to generate bitcoins.

You could just set up your own IRC server.

Or if you want to go fancy (locally): http://wiki.daviddarts.com/PirateBox_DIY

Look into Usenet for a forum with no central control (it's pretty much peer-to-peer, but the "peers" are servers, not any random guy); I have no idea what Bitcoin has to do with anything, though.

I2P's Syndie (http://syndie.i2p2.de/) seems like exactly what you're looking for.

This might be possible; it's similar to Namecoin. I'm not sure how you'd create the incentive to mine, though.

bitcoins should be used for karma.... e.g. you calculate the real time a user spends on the site, a function of the amount of time typing answers and the upvotes they get, and this results in bitcoin karma.

Like Witcoin does? http://witcoin.com