I suppose all sites that have a voting component run the risk of becoming unpleasant.
Hacker News, and we who frequent it, ought to have that in mind.
I think it has more to do with the fact that when you offer zero salary for moderators, you have to take what you can get, and it ain't good. I don't really see a connection to the voting mechanic.
dang and the other HN moderators do a heroic job to set the tone, which has second- and third-order effects on behavior.