I usually give one based of player skill or communication.

If your a tank and you run off at the beginning of the instance before i can Protect or Stoneskin your not getting it. If your a DPS that knows the job well and is actually making an effort to clear the dungeon then ill toss them a commendation. If your a healer and can keep a tank up while hes trying to speed run Brayflox in Duty Roulette i'd probably give you 2 if i could especially if they are in Darklight gear still.

There was a tank i was running with in Duty Roullette i was running as a dps at the time, he was really terrible with holding aggro even though he was level 50, so i gave him some friendly advice on how to keep aggro on large packs of mobs and he took my advice and used it. At the end of the dungeon i threw him a commendation for not being a jackass like most people act when you try to nicely give them advice.