I would like to be able to make a layer unequippable on player death, as it is for beard and hairs.

I thought there were some flags in tiledata.mul which would tell POL to not unequip that item, but I was wrong, or at least, I could manage to find them.

How POL know which layer unequip on death? Is that hardcoded in POL source?
How can I make a layer unequippable?