We heavily use the question bank folders to keep our questions organized. We create them in the banks since it is the only way to keep them from going into an "unfiled" folder.
The regrade feature needs to be allowed for questions linked to banks. If the question is wrong in one quiz, it is wrong everywhere so I fail to see what it matters if it is referenced multiple places. Regrading is critical to fair grading and it makes no sense to either be stuck with a choice between a completely disorganized question database and losing the regrade option.