I always commend the worst person in the group during my roulettes.

Healer who casts a cure every 20 seconds contributing nothing to the run and doesn't have cleric stance on his bar. +1 Commendation
Melee who stay flank whole fight, or better yet in front of the mobs? +1 Commendation
Black Mages who alternates Fire 3 and Blizzard 3 Spam. +1 Commendation
Summoners with Titan Out. +1
People wearing white weapons 20 levels lower then them? +1
Tanks who Spam Flash, and only flash, +1
People who get locked out and have some bizarre excuse. +1
Level 40+ Without the Job Unlocked, +1
Ps3 Players, +1

You get the idea.