One of my biggest pet peeve is when someone constantly drops an AOE on the entire party. Not so much in beginner dungeons but in end-game content like last-boss Monastery etc. It's fine if it happens once but when it happens over and over again and when someone in the chat says "Please don't bring your AOE to the party" and you still continue to do it, why do you still do it? It's probably the very first boss mechanic you learned and you still don't know how it works? I see people running from one corner of the screen going straight to the party with an AOE marker, why?

If you have an AOE marker, bring it to the edge of the universe, don't bring it back to the party and especially don't stack with other players who have it and so help you if you do this on the healers. I don't know if people do it on purpose / as a joke, but you should know better.

If you have a stack marker and only one person is around, don't go stacking on that person knowing perfectly well that nobody else will stack and both of you will die. Instead, kindly die on your own and a healer will resurrect you soon.