This would only be used for certain situations in which a user is experiencing harassment or fights, and they don't want other people quoting their posts so their posts aren't visible as part of someone else's post.
Right now I have it set so a user can put themselves into 'tachy goes to coventry' through their user cp - we call it 'emergency hide', and the members use this if someone finds the board (husband, boyfriend, parent, family member, boss, co-worker, neighbor, priest, etc) and they don't want that person reading any of what they wrote on the boards, they can just go into their user cp and 'instantly hide' all their posts until they figure out what they are going to do.
Sounds like you have it handled. But I would always be afraid that they would use something like that in a way NOT intended. Sooner or later, someone is going to think "I can say whatever I want about that clown as he/she/it can't read it anyway. Hey! Guess what I heard about <insert name here> did with the Mayor's wife!" You get my point.
As good as thre idea sounds, it's things like that that would destroy it.