It's an inoffensive system that people use for which portrait they like the most (because it's the thing you see when you give the commendation) or default to tank/healer unless a specific DPS stood out.
It shouldn't be modified or scrapped, since it does what it's meant to do.

Personally, I withhold commendation for people that don't say "hi/bye" at the beginning/end of a dungeon. :B