Curious Find: Dragonhorn Flute

Just got this quest will digging, it gives 100 rep to Azerothian Archives in addition to the 100 fragments, item stays in the bag after but can't be used anymore obviously.

Eadweard's dialogue upon turn-in:

Oho! Those resourceful little bandits, making use of everything they could find in that tower!
Including, it would seem, the remains of those unfortunate experiments who made it their grave. How delightfully morbid!
The Niffen, of course, have strong artistic and culinary traditions, but you may not know that they have a long history of storytelling as well.
Brigands such as ours would compose epics of their exploits, often accompanied by music and merriment.
They would even engage in battles of poetics, taking turns composing lyrics to insult the other! And the winner was whomever most damaged the reputation of their opponent.
This flute is a lovely physical marker of a strong oral tradition! I shall ensure it finds a place of honor in Loamm.

So.... Niffen have rap battles.

These seem to be one-time-only quests. However, the object that starts the quest can continue to drop as of this date. Clicking on them after already completing the quest returns the standard "you have already completed this quest" text. You should be able to safely delete the item. Hopefully, Blizzard will update the event to not drop these for you if you have already completed the associated quests.