If I go to a shop and look at *all* of my items in campaign mode, are any of those items in use by any of my characters, in either campaign or multiplayer mode? I have a bunch of stuff I want to sell, but I suspect some of that stuff is in use by one of my multiplayer groups.
Select "Unused" for the all-toggle instead to be on the safe side - counts all your current equipped items for all parties as not showing.
I see. So if I sell an item that is not "unused" it will be silently unequipped from whatever character is using it?
Yes. Be very careful. Personally, I don't sell anything unless I can see extra copies sitting there on the screen. This allows extra redundancy to minimize the risk of "darn, I needed that."