Being able to "opt out" of being rescued is as open to griefing too. What about mechanics where the best way to complete it is to rescue (hello world), you could grief by turning it off.

Also, lets opt out of provoke and shirk - can be used to grief.

Remember that debuff called "beyond death" - Well let us opt out of all shields and mitigation then because someone could use them to troll you and make you die.

Almost every skill in the game can be used to grief someone in some way.
Look forward to being kicked from parties or not being allowed to join for having the "opt out" status.