Was Luther’s consort a nun or was she not? Or is it your contention that she was, on top of that, a married nun? My point is very simple: they were not free to marry. All this piling of historical context is fascinating but it does not alter anything in this simple proposition: they were not free to marry, so they were not married. They were fornicating.
What is implied is that someone who was free to pledge the nun gave permission for the marriage. You just don't know about that part.
Regarding Luther, you have to ask him directly ~ shouldn't be long now, eh? That nun is joyfully anticipating kicking you around the block.