Personally, I think it's best to let them stay anonymous. I got negrepped several times at trol posts but that was expected. 2 times or so I got negrepped cause the one negrepping me totally misunderstood my post.. That's just worth a *sigh*

Allowing people to see who negreps you, would probably end up in flaming in quite some cases too.. Don't even try. I support URs idea