My opinion: HN has a particular culture and attitude to discussion that can be grating for non-users.

One example: HNers tend to approach topics as if they have a solid grasp on the context of a matter, and are often negative, hence dang's plea against 'middlebrow dismissal.'

Another example: the common practice of leading rebuttals to a comment with "No. \n" While that's OK here, there are a lot of people who would qualify that as "really fucking annoying."

HN culture leaks onto sites that get linked to by it, and fairly enough, not everybody is down with that.