BUG: Unable to sell not bound exotic?
Try mailing a friend and see if you can add the spear to the email. (You don’t actually have to send the weapon.) If the game doesn’t let you do that, then something is wrong and you should contact support directly.
If you are able to attach the weapon to mail, then there is some sort of trading post issue. It could be you didn’t have enough coin (in inventory) to post the item. It could be you are having general issues with the trading post (and, again, support is the best place to go to resolve them quickly).
Good luck.
John Smith: “you should kill monsters, because killing monsters is awesome.”