Realization

Hold on lemme get the page of the comic

You don't need to three people already explained geez

the healing happens to a pallet as demos pallet is without his eye he cant actually heal it
then valve f**ked over that with scream fortress lore

Demomans eyesore is haunted so if medic does heal demos eye it will try to kill them on Halloween

Because his eye is haunted. Medic heals his eye each year on Scream Fortress, and it manifests into the monoculus.

Demoman glued the eyepatch to his eye as a part of a pirate costume. So, his eye is fine, he was just an idiot.

thats not it that was a theory

Oh.