So no harm to run in 5th?
I think you're misunderstanding what that means. When it says "5" it doesn't mean you are in 5, it means that's the highest gear it will allow it to shift to. For example, if you bumped it down to where it showed "3", it would shift 1, 2, 3, but would not shift into 4th. They call this ERS(electronic range selection I think). So if you put it to "5" it will shift normally, the only difference is that MDS will be disabled.
EDIT: and no this does not harm anything...