Piercings nothing near the act of cutting a animals toe off at the first knuckle. It is not a trauma like declawing, if it was tnr would not tip a cats ear to show it has been fixed. A cat can easily live a comfortable life without the ear tips, a declawed cat is mentally traumatized and will live in pain for the rest of it's life.
What it is, is disrespect to the animal and a possible entanglement risk, this goes for chains and collars not made for a cat. Been called out too often to strangled cats wearing jewelry chain or small dog collars. (Used to do animal control)
BTW Piercings will just rip out of a cats ear. And often just lead to infections. Some places it is legally considered animal abuse. Sadly many places STILL allow declawing.