Warning! Spoilers for the Demon Hunter leveling zones below!
There's something I've noticed in the Demon Hunter leveling zone.
The quest "Enter the Illidari: Shivarra" has the player make a choice between 2 options:
1. Sacrifice the blood elf standing at the altar
2. Sacrifice yourself
When you pick option 1, nothing special happens. The quest simply concludes.
If you choose option 2 however, your character dies. Upon spawning as a spirit at the nearby spirit healer you get a prompt from Illidan, telling you how you must have an "immortal soul" like he does (a soul like that of a demon).
My problem with this is as follows:
The quest takes place on Mardum. This is very significant since it's pretty much the most fel infused planet to have ever existed (to the point where it "appeared in the distant reaches of the Great Dark as a burning star"[1]).
We know 1 thing about the immortal soul of a demon: If a demon dies while in the twisting nether or a location heavily overflowing with fel energy, the soul dies permanently[1].
So, considering our Demon Hunter died in a location extremely saturated with fel energies (literally volcanoes and rivers of fel), why does our Demon Hunters soul not perish completely?
Sources:
[1]: World of Warcraft Chronicles Volume 1 pg. 23