Is the problem that the community isn't telling the problem person that they're banned? There's a reason they don't: because by and large, when you tell someone they've been banned, they react (particularly in the heat of the moment) by throwing a temper tantrum with a new account. Again: why is it the obligation of the community to absorb that kind of abuse?
And therein lies my double bind: how does one balance the need for a civil community with the hacker's dislike of things done in the shadows? Are you happy with the idea that users are secretly banned all the time?
Failing to welcome the comments, well intentioned or otherwise, of someone who had to be explicitly driven out of a community is not a terrible thing to do.
Not all of those [dead] comments are actually from hellbanned users, are they?
How about, the ones who care enough to put contact info in their profiles, you can reach out to them and say "you may not have noticed but the HN admins seem to have banned you".
I have contacted dead accounts in the past, a problem is that it’s hard to get contact info.
Hellbanning spambots I can understand. Hellbanning people?