@kravpoker makes some good points. They can mess up with instant message also, like when a player is busted off the tournament, somebody can instant message “good bye”, “see you”, “thanks” etc.
Rude play can’t be quantified, like some people raising pre-flop, and folding frequently, player in hurry, high bet and clear up his stacks while bringing down few others in that time, or even some play just to do that. Then why counter reacting verbal comment alone should be quantified as rude.
(Added: I think this is what Replay does, deciding as rude based on what happened, if you could read this post.)
In my personal experience, I see people tend to take the rude comment (even in genuine cases) personally, rather than its the game that we are commenting. I generally avoid them now.