Originally Posted by
Iscah
The problem isn't just ears, but hairstyles. For whatever reason – maybe because they originally planned no hats, or maybe some more obscure technical reason – they built Viera hairstyles so they can't "break in half" and hide only the top part, as usually happens when a character has a hat equipped. They can only wear headgear if all or none of the hair is visible, and the ears have nothing directly to do with it.
It's why they're able to wear things like hoods, and why what does and doesn't work is so patchy. They can wear the level 90 reaper hat (bindings cover the hair underneath) but not the level 90 red mage hat, or can wear the hoods from the Rinascita gear series but not the berets.