What are the decent alternatives? Or else, let's try to make this into something better, by flagging instead of commenting, and downvoting racist, sexist, bigoted crap instead of feeding the trolls.
Metafilter, as you said, is one example. Another is the Ruby Rogues Parley mailing list (now Discourse site). I can only imagine what a HN with similar filtering-of-the-noise would be like.