Not addressing the real heart of the issue, but strictly from a technical point of view: A message does appear in Chatterbox now when someone is borged, with a random punch line, like
NodeReaper has swallowed Elian. Elian was tasty!
I'd prefer to keep the message coming from NodeReaper (hey, we could use a little more humor) but it would be pretty straightforward to privately /msg the borg-ee with something like
root says You were borged by Elian
Now, as to the "should": to me this would be a reasonable compromise. I think it would be only polite to tell someone privately who chastised them (I sometimes /msg people when I downvote their writeups) but I don't really see the need for an audit trail.
It's only chatter, for root's sake...