Ask PG: Showdead has lots of constructive comments from hellbanned users. Why?

After turning on showdead, I tend to notice that there's quite a few comments that weren't there before that don't seem to be spam and are often times quite insightful. From clicking on the username that posted them and then looking through their comment history, it's clear that they've been hellbanned and nothing they say will ever be seen with the default options (or by a web crawler).

Admittedly, there may be a reason for this that isn't obvious, but it still doesn't seem right.

Is there any recourse for these users? Should they be notified of their status in any way, since they may post with the intention of getting responses?