Wrath.

Quest still shows on turn in too. (=

We really need the quest IDs on these kind of reports. It could be there are two different "An Unholy Alliance" and you picked up version A, but version B is still shown.

uh.. -points at the title-

the quest id is there?
unless there's a way to get quest id's in the tooltip for the marker on the npc?

Well there are four different "An Unholy Alliance":

https://www.wowhead.com/wotlk/search?q=an+unholy+alliance

Most likely we show the wrong one on the map, but the quest that can actually be accepted is a different one.

Looking at the chat in the screenshot it will be these two quests:

https://www.wowhead.com/wotlk/quest=14353/an-unholy-alliance
https://www.wowhead.com/wotlk/quest=6521/an-unholy-alliance

can we add (or is there already) an option to show quest ids (like the levels) in the tooltip for the questgiver?

It already exists in the Advanced options.