I like Metafilter's discussion as well. I think the key is having fairly heavy handed moderators who are involved in the community. That keeps discussions civil

I like Metafilter's discussion as well. I think the key is having fairly heavy handed moderators who are involved in the community. That keeps discussions civil and on track, and it also tends to drive away the "harassment-as-free-speech" people who create a lot of the toxicity you see in places like reddit and twitter.