I think if you accept it then “untrack” it the problem is solved. At least someone explained that to me as something I must have done which resolved this problem.
I remember when I was creating alts for SL I would always go to Dalaran for the extra heartstone because it was easy for me to go to their transmorg then use my regular hearthstone to go back to SL. Of course that bird was always following me around.
So I accepted the quest, “untracked” it and that solve the problem.
Mizzen stopped spamming me after one of the many hotfixes in those first few days finally allowed me to finish the event, but I’m still finding invitation bags in the inventory of alts that I apparently set aside instead deleting while trying different strategies to get it to stop.
Usually by the time I have that many quests I’m on to the next expansion or at least the next release and I delete the old ones. But other people’s mileage may vary.
if you accept it. Do the initial “turn it in to blah blah” quest and then DON"T take any other quests it stops the spam. I stopped getting them in my mail after that initial turn in. Deleting them just resends them I noticed.
If you’d said something like, “Hey, just FYI, the quest log limit is now 35! Your point still stands, but at least there are ten more slots to fill before it becomes an issue,” it might have come across as “genuinely trying to help,” rather than snarky.