Quote Originally Posted by RedHeaven View Post
In other games, I would use private messages while in a random dungeon group to gently give another player some advice, without the possible risk of embarrassing them in front of the rest of the group. It could find a similar use here.
You could also use private messages while in a random dungeon group to provide destructive feedback to another player, without the possible risk of getting called out by anyone else in the group. Followed by "I have no idea why player X just left the instance".

The potential for abuse is as great as the potential for good, and more tempting to frustrated players.