I'm all for insulting people who abuse the system :-). And for putting trivial inconveniences in their way, if nontrivial ones are too difficult.

And presumably, indeed, reversing all someone's votes isn't currently supported by whatever LW admin tools there are, and implementing that feature would be a non-negligible cost to weigh against the ability to disincentivize abuse in that way.

(For the avoidance of ambiguity: I meant "undo", not "reverse the sign of". It would be quite amusing to reverse the sign of all someone's votes as a punishment for abuse, but I can think of more than one reason why it probably wouldn't be a good idea.)