You can always say, "Hey bro, your skillz are mad bro, I enjoy playing with you bro, I'm in a party so I can't commend you bro, if you were a potato based food bro you would be a tater tot bro, because tater tots are the best potato based food bro." I suggest making a macro, since you may not want to type it all out every time.
Really I agree you should be able to commend folks as long as you didn't que up with them, but just like the duty roulette, it was implemented pretty quickly, and they have said they are looking to let multiple people que up for roulettes together maybe they can work this in too.