Something that really turns my stomach is seeing masks worn just below the nose. It looks so unhygienic, and people will keep touching the top of them right by their nostrils, then returning their hands to their phone or whatever. I've never noticed before how ugly noses are anyway, but seeing them poking out over the top of a mask is just gross.
and also as such, makes the mask useless ! (as are the disposable ones being used for the 4th and 5th time, after being in a pocket / purse etc)