Canon or not other MMOs have an option to disable helmet appearances for being overbearing, and having a murmillo helm on a school uniform, a pirate costume, a ninja, a lot of anachronistic things can happen like how monks with beak masks are a thing.
A visual buff indicator that a helm has been worn is an alternative to show they’re under the influence of the helmets. Unfortunately that might not happen so my hats will always be covered by a gladiator helmet.