The problem with hell-banning is that for users that post a lot of comments, they'll soon realize that they are hell-banned and trolls (in particular) can only be stopped if they are genuinely ignored.
For this reason, if you want to stop trolls, slow-banning could be a good alternative by making usage of the site unpleasant. This way they can still interact with others, but it will be painful for them to do so.
I agree that these methods are passive-aggressive and shouldn't be used on non-trolls, even if such people do not comply with the community's guidelines. The problem with this site is that user accounts do not have emails attached ... as a much more effective method for making most users behave according to guidelines would be to send them a warning.
"why did that user get banned?"
"they were a troll"
"ah, okay. that's fine then, seeing how I am not banned this must be totally legit. damn trolls!"
What if users had a killfile for their account? Seems more meritocratic than hellbanning at least, if I can just choose who I want to ignore or not, and if you can tolerate someone, then they're alive for you.
Most sites have a capability where they can flash a message to a user the next time they log in. Such a message could link to the flagged comment in question and point out what was wrong about the comment.
But really, HN is not a democracy, or transparent, or really anything other than pg's playground. So it's up to him, and clearly he's chosen to put avoiding confrontation first.