I always saw commendations as a relatively simple form of positive reinforcement, basically a tap on the shoulder saying:"I like what you did. Keep doing it."

I don't really like the idea of using it for matchmaking and would likely be much more stingy with giving out commendations. Right now, I often give out commendations to players that played well even if I don't know their attitude because they didn't say much (Or anything beyond "Hi/Bye"). But I find attitude to be very important if I'm to play with them more often, so I'd think thrice before putting them into my "favored" pool. The issue is even bigger in short duties like Guildhests or Trials.

I can agree it would, at times, be nice to be able to do something with the comms you get. But given the fickle nature of comms...I'm not sure what's a good thing to do with them.