I have a somewhat oddball answer to this question (sorry for jumping in mid-discussion, too), but I would say Tolkien intended the description of Durin's bane to be ambiguous, using phrases like "Its streaming mane kindled, and blazed behind it" as well as the celebrated two "wings" lines... "mane" can imply something either bestial or human, and "kindled" can either evoke a mane which is
on fire or one
made of it... similarly, he creates uncertainty by first referring to the shadow being
like wings, and then simply referring to the "wings". If anything, verbally, the shadow-wings are given a heighted solidity and reality by being referred to this way (or, if you prefer, the real wings are lent an aura of uncertainty and insubstantiality.) The Fellowship probably couldn't tell whether the wings were real or not, and, by making us see through the Fellowship's confused viewpoint, Tolkien allows the reader to experience some measure of their fear and unease.
I other words, no and yes.
