Just genuine curiosity because I like this site and like how active you are in constructively moderating it: Why not simply ban people who have crossed the line this badly for this long? It certainly doesn't seem heavy handed or unfair.
The idea that commenters should "make HN good because we all want it to be good" is quite positive, and that sentiment seems to be reflected here far more than banhappy reddit.
It's better to err on the side of patience generally, and feels more in keeping with the values of the site. There's are also judgment calls about things like who seems more likely to respond to persuasion, how much history the account has, whether it's related to previous abusive accounts, and things like that.
They'll just make another account and start over.
By explaining what the person is doing wrong, maybe Dang can help them be a more productive member of the HN community.