Block means I want him GONE

People who are blocked should not show up on the on/offline list, or anywhere else. If someone's blocked, it should be, from the point of view of the person blocking them, as though they did not exist.

There should be an exception in the permissions system for admins; possibly it should not be possible to block an admin.

There may need to be an intermediate level, call it "mute," that preserves presence so that people who are being stalked can detect their stalker.