Undo should be disabled if a user is out of time.

[rrabien]

Undo should be disabled if a user is out of time. You can't kick the user since they are still making moves. Make a move, undo, move, undo, repeat. Run the clock down and there is nothing you can do.

Or, remove the 20 second wait from the kick button.

[Caffe Latte]

I think if I'd face this type of behaviour, I'd just quit that game. Karma points are very easy to be recovered soon.

[aesche]

Mutual abandon works as soon as the opponent is at -0 sec, afaik, giving his permission by default.