I think that a huge part of it is simply the amount of people here. There are some pretty unfocused subreddits that are decently small and end up with a lot les

I think that a huge part of it is simply the amount of people here. There are some pretty unfocused subreddits that are decently small and end up with a lot less BS than you might have in HN (esp. threads about Uber, Code of Conducts, etc.) The moderation, of course, plays a huge part too though.