That already is a rule
And wtf I know we had it written down somewhere. Any form of purposely getting yourself teamkilled is/was a bannable offence.
@mikey, its one thing when it disappers, its another when you ignore it. Ignoring it prolongs the match and leaves the other player wondering what stratagy to use. Just hit 2 if you dont want to knife. The other player usually is camping waiting for a response.