Syag, what is the difference between supermarkets and any other place? Either way, according to your logic, you are highly unlikely to infect anyone, so why ever wear a mask?
The problem with going maskless is that even if you are correct that won’t be reinfected and won’t infect others, unless someone knows you or you wear a sign that announces you as a covid survivor, other people see you as yet another maskless person. They can’t separate you from all the other people who rationalize without evidence that the frum world has herd immunity; or who get deeply scientific and argue that if there was no mass outbreak over the last three months, then obviously it’s over; or who cite various third hand reports of rav such and such who told someone the mageifa is over; or because deblasio and cuomo are untrustworthy idiots anyway. It becomes a self reinforcing cycle of communal complacency and includes people who can and probably will spread the virus. I know plenty of people who do not have antibodies but do not wear masks because no one else is, so (as they explain) obviously one or more of the above theories are correct. They do not differentiate between venues except maybe to the extent that some stores insist that customers wear masks.
People who are concerned about getting infected are then faced with the unfair choice of taking additional risk when they go to public places or alternatively of not participating in something they have every right to participate in because no one else is taking precautions.
It is hyperbolic to say people with antibodies are murderers for going maskless. At the same time, they are contributing to an environment that unnecessarily increases the chances that people will die and/or that unfairly keeps people in lock down to avoid other people. What gives someone the right to prevent someone else from going to shul or to work. Contrary to what is being promoted on these message boards, it’s not at all an exercise of personal freedom. It’s an aggressive act that prevents someone else from acting freely. It’s not like drinking cholov stam because you hold cholov stam is ok. It’s like pouring your cholov stam in the communal vat of cholov yisroel milk because you hold it’s ok.
What I have a hard time understanding is that much of these debates are over masks. It’s uncomfortable, but wearing one is not exactly mesiras nefesh.