This seems to be a bug that concerns every item in atleast Albion usable in left hand. I've checked the feather merchants, reg merchants, crafted items, housing search function etc and not a single item usable in left hand display any information that it's usable in left hand, neither in the toolbox nor when you delve the items. Makes it very hard to for example buy a feather item or a crafted item from housing without first looking up online which of them are left hand usable.