Sometimes I check the comment history of these dead posters; 80% of the time it appears like they are a genuine troll who was correctly moderated out of the community, however, a significant portion of the time, there doesn't appear to be anything particularly inappropriate in the comment history, but the user is still doomed to waste a considerable amount of time attempting to contribute to this board.
In the context of internet discussion boards, it seems a little harsh.
Off the top of my head, I feel like something akin to an automatic probationary resurrection period would be an interesting idea. Perhaps it occurs one year after hellbanishment, giving the community a chance to organically reevaluate the user's quality of contributions, and giving a second chance to those who have matured in a years time (or who was simply hellbanned in error).