I assume that facebook allows everyone who can see an original post to also see every comment. It didn't used to be that way which led to some odd threads where people didn't have the ability to see every comment that was posted to something. It actually makes sense but I wish facebook was more clear about the fact that this is how it is (if it is indeed how it is.) But my profile is locked down pretty tight so even if some friend of a friend thinks I'm a wackjob and wants to they can't come to my wall and start spouting off on my status updates because they can't see them. Nor can they see who my friends are.