BMW adding the M badge to the 235i is done for no reason other than to make Lorenzo the hair stylist feel like he owns an M-car. Which is the exact reason why some idiot with a 330i would add the badge to their car. So why does BMW get a pass but the other guy doesn't?
In any event, it doesn't bother me in the slightest. I wouldn't do it, but I'm not going to show up at the guy's place with a pitchfork + angry mob and berate him about it either.