Ask HN: For a simple forum, should I use bbPress or is there a HN/reddit style one?

I'm thinking of starting a discussion forum over at my Gifty.co.nz website. I've never liked heavy and ugly phpBB-style forums. I'm really keen on simple and minimalist, so I like bbPress. And PunBB looks okay.

But something with the simplicity and threadedness of Hacker News or reddit would really be great.

Does anyone have any ideas or experience?