I was thinking about this for quite some time now and it would make admining a server a hell of a LOT easyer!
Firstly you could simply mute the chat of a troublesome user.
I'm quite for this and also an option for normal players to localy mute a player would also be good. That would come in handy if a player does not like a player in game and he could mute him.
Admin mutes would be global.
Also i was discussing this with exposed and he was quite for this idea.