People will commend or not commend based on their own personal criteria (which is how it should be), I for one always commend since I don't see the harm in giving someone a little something extra for their time. I base who gets my commendations off of attitude and sociability, whether or not the person cares to respond to me or if they could care less about what is going on and simply going through the motions.

What happens is roughly secondary, if people are inconveniencing other people they'll be low on my list. I don't commend tanks who don't dodge for instance or DD who try to pull more than the tank is comfortable with. If it is someone's first time and they do well, I'll usually throw a commendation their way.