Usually skins should be black when they have pixels that are completely transparent. This mod instead removes limbs if they don't exist and can make the player unrenderable.

demonstration uploadable skin

What happens when worn and F5 third person is pressed:

Sorry, I forgot to get back to this, but this issue has since been fixed in version 1.10.0 of Kirin over here: MineLittlePony/Kirin@8aac40e

The feature that enables transparency on skins is now opt-in by mods, so this issue will only occur when you're using Mine Little Pony.

Release notes for 1.10.0 are over here: https://github.com/MineLittlePony/Kirin/releases/tag/1.10.0 (it's the most recent for 1.18+)