I really don't know. I've not traded in a Stock that went all the way through the Bankruptcy process, before, so I have no previous experience to go on when it comes to a stock that is still selling even after it has been "officially cancelled". Just simple logic tells me that you shouldn't be able to sell something that no longer "officially exists", but, obviously, MMs are still doing it.
So, IMO, something "strange" is going on, here . . .