While I can't speak for zedshaw, I think the problem with HN is that while it, as you say, shuns and bans anyone who speaks in an aggressive tone or who directly vituperates others, it also allows (and often supports, with upvotes) one to completely slander someone as long as they do it in a calm and reasonable tone.
As an example, specifically regarding anonymous accounts and zedshaw: https://news.ycombinator.com/item?id=9276436