> Staff seem to get infected less frequently than other diners, even though they are in the space for longer. There are a few possible explanations, but the fact that staff don't take their masks off is a pretty compelling one.

IMO that’s the least compelling reason. One big one would be the staff having way more contacts and thus higher exposure to the other circulating hCoVs as well as SARS-2 itself.

The evidence for face masks is weak at best. In my opinion they don’t even make sense theoretically unless you pretend that droplet transmission is the dominant transmission mode, which is completely unproven yet widely believed dogma (go figure)