... A mask is designed to protect other people from you, not you from other people. For the most obvious example, a surgeon wears a mask to prevent their germs from getting into the body of the patient they're operating on. If I am wearing a mask and the person I come in contact with is not and starts breathing all over my hands/arms/face while I take their temperature/etc (some of them even touch me when I've repeatedly asked them not to), then I am the one at risk.
Proper pandemic etiquette: assume you are contagious and that to prevent spreading your assumed illness to others, put on a mask (ideally also wear a face shield and gloves, they can be purchased in packs), don't come close unless you have no choice, minimize physical contact with people, surfaces, and objects, wash/sanitize your hands before and after any sort of public contact, keep an eye out for even minor symptoms, don't linger overmuch in public spaces, avoid people at high risk, do not pick up products you aren't going to buy, sanitize your commonly-used devices/buttons/switches/knobs/writing implements/tools with hydrogen peroxide solutions.
It is also a good idea not to eat or drink in public spaces, and never sneeze into your hands; use the crook of your arm. Press switches and open doors with your sleeve/elbow/waist if possible. Keep a spare mask on your person in case the one you're using breaks.
Edit: Remember that you're doing it to protect other people and therefore your own good health is not a relevant excuse. There are people who can't do this stuff (people in wheelchairs can't push open doors with their waist, people with cognitive impairments have trouble wearing PPE and following all advice, people who need oxygen cannot wear masks, etc), so if you are able to, you are obligated to in order to protect those who can't. It's worth pointing out that the people who most struggle with these advisements tend to be in the groups at most risk.
If you have any questions this did not cover, I can try and answer them.
I doubt Rev will respond to this (at least not in any meaningful way).
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What's the difference between a pickpocket and a peeping tom? A pickpocket snatches your watch.