Dang and the other moderators here are incredibly scrupulous. If you browse with show dead on, and find an account that is posting regularly but banned, and go back through their history, you'll almost always find multiple warnings and a public statement about their banning.

HN has problems but moderation being arbitrary isn't really one of them.

It's the anonymity and odd changes in who is moderating that makes it feel different. Standard setup to me would be consistently opinionated person, or team with some central directive (and hopefully oversight).

I was banned from /r/comics for saying a comic wasn't funny. Hacker news doesn't ban anyone for such stupid reasons.