Hmm sounds to me like some users have the warning thing backwards. I don't recall ever getting a warning that my email address will be visible. The only notification I've seen is that it will NOT be seen. If no such thing is notified, then one should assume that your email address might be visible to others.

I understand how this can be overlooked by someone, but it would still be that person's fault, and not the systems. The possibility of removing the user should however be present, imo.