I will let them know the horde they just killed is my main and im simply returning the favor. They will completely ignore their actions and continue to belittle me for "needing a 90 to kill me because you're bad!" So far in my adventures MOP has really shown me the level of maturity on this server. A Pally named Massacre for example killed my main. I log on to my 90 kill him and all his friends. They eventually overwhelm me. He sends me a real-ID request with a message on how pathetic and fail I am to lose to HIM at 85. He ignored the other 2 players plus mobs beating on me. He then decided to let me know how in season 9 he was the !@#$ with 3 thousand twitch followers watching him smash all the top players in arena.
This guy was pissed. So I killed him many more times as he was saying everything he can to be as insulting as possible. Eventually he logged off after I fell silent and just chased him into a safe haven. This expansion really did expose people who need to be on PvE servers. Kill me all you want, ill return the favor, but dont real-id friend me just to complain because things didn't end up in your favor.