I would argue that all long finned Bettas are harmed by their fins, and that the whole fancy Betta business has a cruel edge to it. Unnaturally large fins are not always supported by the body. Ever since I kept wild Betta splendens, which are not beautiful in the same way as the man made fish but are marvels of speed and balance, I haven't been able to look at a store or hobby betta with anything but pity. The fish struggle to swim.
I know I'm in a tiny minority, but you did ask, and this would be my answer. I think the level of mutation in high end Bettas has taken them into the ugly realm of celestial eyed goldfish or other disfunctional linebreeding products. There's money in them, and if you buy 'feathertail' females you'll spend a lot for fish with largely hidden genes. It's the males who express the deformities. If I were a breeder, I wouldn't sell the females cheap, as bettas are easy to breed, and someone with diligence and a willingness to work at it could do something commercial with them.
If I were ever again tempted to breed fancy Bettas, I would start with plakats, because the fancy breeding has aimed more at colour than at gargantuan fins. They can at least act like fish and aren't in danger of death from infections starting in the folds of their fins.
I know that's a hardline, tiny percentage of hobbyists view, but I would love to see the "over bettered bettas" fade out of the hobby.