I see alot of people say no rep messages/comments/hidden/invisible text etc.
But noone has made a rule against changing your user-group name (donor perk)
ie: Player changes his usergroup name multiple times to give messages to people currently playing
player 1 has usergroup name "Keeper", notices player 2 goes offline and player 3 is online, makes message to player 3 by changing usergroup name to "Bodyguard" and changes it back later.
could even be used as secret means of communication between players by sending usergroup messages to eachother