Spring32 
"[@ZippySqrl":](/images/2465020#comment_9311943
)
Not the show but mostly the logical thinking.
If you can’t heal and fix the bones inside a wing instantly, and make regrow the horn of someone, why you should be able to change someone’s internal and external anatomy permanently and out of nowhere? If it is possible, I highly doubt it is permanent. Even the breezie transformation was timebound. If I were Twilight i would have never risked to use a spell Which effect was limited in time, if I were able to have a permanent one and then revert back once I desire.
Also, there would be no ponies without horns or wings if magic was able to permanently change someone’s anatomy. Also why the need for x-ray, hospitals, doctors and so on?
So imho is more likely that magic cannot reach that level of biological craftingat least permanently. Maybe, those who are able to do that are really, really, really rare, and the knowledge of the thing is nearly forgotten by the common people.
Wintermute
Not the show but mostly the logical thinking.
If you can’t heal and fix the bones inside a wing instantly, and make regrow the horn of someone, why you should be able to change someone’s internal and external anatomy permanently and out of nowhere? If it is possible, I highly doubt it is permanent. Even the breezie transformation was timebound. If I were Twilight i would have never risked to use a spell Which effect was limited in time, if I were able to have a permanent one and then revert back once I desire.
Also, there would be no ponies without horns or wings if magic was able to permanently change someone’s anatomy. Also why the need for x-ray, hospitals, doctors and so on?
So imho is more likely that magic cannot reach that level of biological crafting