Is there any way to get quest items out of my inventory? There are several things which I know I will not use anymore (such as the House of Ballads armour) but it just sits in my inventory cluttering up the interface.
It seems to be an ongoing problem. Sometimes some people are able to sell the quest items, sometimes people can junk them and sell the junk, sometimes they are just stuck with them. Reloading the game may or may not fix the issue. There are several forum posts similar to this discussion with people having the same inconsistant batch of problems and solutions.
My THEORY: When you do a quest that awards you with a weapon or armor that you need to complete the quest, it may glitch in your inventory if you stashed them in you home's chest before looting them again. So when you "re-loot" the items, the game believes you're on the quest and you haven't completed it yet. Thus, it's a quest item again.
If you wish to sell the "quest-given" items in your stash, drop them to your junk while you're browsing the stash chest. That way, they go to junk, and not your inventory.
[I also believe that it will avoid making the item soul-bound to you. Sense you can remove them from junk later to use it. But I haven't tested it yet.]
Of course, SAVE before doing anything, anywhere, anytime. Have extra saves around. Some items might or might not get stuck in the inventory.
That's the only way I found to avoid any "accidents" like I've met with my Shine and Shadow daggers. But that's ok, it's just one sticky item at this moment.
P.S. If you want to read a book or a scroll, I suggest reading it while examining it. It have an extra button to "read" it without looting it. Some quest items got stuck in my bag as well, some that don't even relate to any that I've done. I'm not sure if I missed a quest somewhere, or it's just a bug. So watch out and don't pick up any scrolls or books that you don't have the quest for.