Who's to say how polite one is, himself or others? 
If one can chose his setting, its not hard to guess that everyone would be polite ones.
And if you(presumably) thought that other would create your "polite" mark, then I think it would be abused for sure.
You'll get bad sportsmanship remarks just for winning a game, or if your opponent would blunder a piece etc...


I just realized that it would be cool if any member at chess.com will get one more feature saying how polite/rude he/she is. I know it could be difficult to do (even to design the feature), but it would be so nice to play (especially live chess, where emotions overfill us) just with polite gyus.