What is happening:
Every item that is given by a quest is considered a quest item, and therefore cannot be sold, worn, or interacted with in any way, making many quest rewards quite useless.
What should be happening:
Only items needed for continuing a quest or for another, separate quest, should be considered "quest items."
Steps to reproduce the issue:
Attain any item from a quest
Game client version:
64-bit Linux Mint 18.2 Cinnamon