Ask HN: Forums with quality discourse

What other forums have the same quality of discourse as HN had (and on occasion, still has). The topic doesn't necessarily have to be start-ups. I want a site that has, like HN's guidelines state: "anything that gratifies one's intellectual curiosity".

Academic Hacker News had potential for a place for a good community. Arc Forum has good discussion, but I'm looking for something more general.

I read that, after the quality of HN fell heaps, some elite users left HN for some greener pastures. Where did they go?