Add PM for promotion to TL3 (to be consistent with TL1 and TL2)

I do that for some new users but it seems like a sledgehammer to crack a nut. It would be better to have a site setting just for moderation per user. I might add a feature request for that (though I have a feeling that it’s been asked before).

Back to TL messages, it would be good to be able to control these completely, eg turn on/off and edit messages for each TL.