Tested with a few (3-4) items now.
Moving a character bound item from character bank to account bank seems to delete the item.
It will still pop up the prompt that you "cant have character bound items in the account shared bank", but the item disappears from the character bank, as if it was moved.
It is not in account bank, character bank, nor inventory.
I didn't lose anything too major, but someone is going to not be paying attention and get something like SoS deleted.