There is moderation behind the scenes. I've had some of my posts edited to improve them. Also there are a number of rules about how HN works that I suspect some people are told and others are not.

HN also forbids the discussion of what CNN considers news. We don't have endless knock-down-drag-outs about the usual subjects.

Also HN has a fairly unique community of people who are interested in both technology and business, no matter where they are located.