So on top of Ratchet tail biting, I get to add my sister's veil tail, Pantelaemon.
We noticed his tail disappearing when he was in the 2.5 gallon with a filter and thought that maybe he was getting caught. Eventually my sister decided he was probably tail biting out of boredom since he's a pretty social fish. We moved him into my split 10 gallon so he could see other bettas (He doesn't flare or hide so I'm assuming he wasn't stressed at all. He was also building giant nests like crazy).
In my 10 gallon, he somehow found a way to split his anal fin in half (up to his body). Changed the water and changed out plants from his section with the other two sections, and he managed to tear his dorsal fin in half (down to his body). So, to combat this since it looked like he was just going to keep tearing his fins and because he managed to get a little bit of rot going on his tail, I moved him to the hospital tank with 1 tsp/gal of aq salt. And then, when I check back on him, I saw that half of his remaining tail was gone with tell tale biting.
So, Pants is now officially the stupidest member of our betta group. If there's a way to hurt himself, he will find it and do it multiple times. If there's a problem to be had, he will have it. If there's a chance to scare us into thinking he has ick or popeye, he will scare us.
Tail biting sucks.