[Morsul the Dark]

Ok lets think this through morgoth mocked life right?

Orc=elves
trolls=ents
balrogs=???dragons possibly

if this is true we can assume balrogs have wings on the basis that dragons(most notibly smaug) had wings and as for wing folding that depepends on the wing strutcure it could indeed fold quite tiughtly though i do agree that is a dangerous blow to the wing theory however considering a balrog flight is quitew possible with wings thinking it through most biords ride on air current which has to do with hot air and such doesnt the bakrid provide its own rising heat to glide upon.

Scientificly speaking were looking at raptor like wings made for gliding not so much flapping which would make them more leathery and in fact thinner because there would be less need for muscle in the wing which in turn would make it easier for the wings to be folded into smaller area of space.

Another thing however against wings is the fact that balrogs live underground(Im talking moria if you know more about other balrog locals please tell me) and if all balrogs were to live mainly underground isnt it in fact useless to form with wings.

However no conclusion ever will be reached I myself believe balrogs have wings.