I believe he meant the sender's own e-mail address. That is, just because Rokman wants to e-mail Dirk, doesn't mean he wants Dirk to know Rokman's own e-mail address. Rokman trusts the site's server (from which, if permitted by config.php, he could delete himself at any given time or change his address) but not human users.
So basically Rokman wants the trust worthy site to be used as a middleman between the sender and the recepient. Kind of like a ticketing system that either uses a temporary internal server e-mail address to reply (the site would then forward the reply to the real original sender) or contains a link only through which the recepient can send a reply.
If it's any consolation, Rokman, even without all of that you can already hide at least the admin's e-mail address (the one in config.php which the site uses to send messages itself).
Just use my submitted patch that divides the admin's address into a public address (for admin notifications) and a dummy address (for user notifications).