How do items become spiritbound and is there any way to remove it once they have?

Spiritbound equipment are special equipment designed for a specific charecter.
This may be a quest item / reward from the Main quest line that is not intended to be given away / Sold, but to be used to progress your game.
There is no possible way to remove spirit bound off an item, equipment, or consumable.

That's not what I'm talking about. I got an orange weapon and enhanced it thinking I could still put it on the market but now it is spiritbound.

Okay,
Than you will need to build an extractor at your camp, and raise it to an appropriate level to take the stones off to be able to re-sell it on the market place.

How do I sell spiritbound items I have a bunch of spiritbound items that if sold I'd get 100-200mil silver