Following the ""What strikes us today as bizarre might not have done in the 18th century and earlier" idea; it doesn't seem impossible to me that, in some cultural settings, giving an animal silver or gold replacements for body parts might have been seen as a generous upgrade! Stranger things seem to happen in mythology: for example Nuada was entitled to reclaim his kingship of Tuatha de Dannan when he had a silver arm fitted to replace his own one, lost in battle.

On another point, I agree with Jim Carroll both in finding the wording "occasionally work their way down into oral tradition" from classical sources, (rather than having sometimes worked down from oral tradition into the hands of the classical authors) condescending and also in doubting that the first publication of a song is all we need to explain and date its origin. Nevertheless I do think that plenty of classical material picked was up and used within the oral tradition. It only takes one link in a chain to have been exposed to the literature. I have read that the hedge schools may have introduced many classical ideas into Irish songs – some of the Napoleonic ballads spring to mind in particular. In other words, I don't see why the exchange couldn't have been in both directions (including starting in "folk" tradition, being trapped for a while in classical literature and then being reclaimed by "folk"). What does seem to me logical however, is that over years of being transmitted orally, what is retained in a song is that which has meaning and significance to the singer. If talking animals, golden wings etc weren't important, why were they retained? Clearly in some versions the supernatural aspects were edited out so perhaps they didn't mean anything significant to the "carriers" in that line but perhaps they did to other carriers in other lines of transmission.