Launchpad handles this nicely, in my experience. You register for an account, and that account has an email address (or multiple email addresses) associated with it.
Bug reports do not inclued the email address of your account. In order to see someone's email address via the web you (at a minimum) must be logged into your account. Normally, bugs are viewed/edited/posted via a rich and expressive web interface, however, if you really want to make modifications via email, you can do so, as long as you send the email from an address on your account. Launchpad then performs the corresponding action, stripping your email out of the spam-harvester-viewable record. Best-of-all-possible-worlds, as far as I can tell.
