If the officers wear markings there's no reason the medic (and other specialist staff) wouldn't wear markings. More "civilized" or extremely honor-minded regiments would probably find it offensive to not wear all the marks you're entitled to, as in badges/buttons/symbols. And some would not for whatever reason. Catachans don't seem too big on markings, maybe because they're all brothers from the same tribe or something. Ragtag penal troops or low-morale regiments won't have many markings since they either don't deserve them or never learned to use such.
True but in like all war movies once soldiers reach the battlefield they stow their markings to prevent snipers from knowing the highest ranking officer and working their way down. My uncle said the only time he wore his Seargent patch was when he was on base.