[tlb]

I wear masks in public, even though I have no comorbidities, because of all the people I might subsequently spread it to if I got it. Remember that asymptomatic transmission for several days is common.

Putting on a mask takes a few seconds, so compared to all the suffering it might prevent, even at 0.01% probability, it's well worth it.

[clairity]

no one is arguing that you disregard others, especially those who have comorbidities, only that a mask adds negligible risk reduction outside, above and beyond the natural physical distancing of strolling down the sidewalk.

risks differ with context.

[tlb]

Do you have evidence that risk reduction outside is very small? I haven't seen any, and I think it would be nearly impossible to collect such evidence.

A plausible rule of thumb seems to be: if you could smell someone's cigarette smoke, you could inhale their viruses. I certainly smell smoke from smokers I pass on the street.

[clairity]

there are no studies done, because, as you note, it would be difficult and costly, and it's a simpler (and more easily followable) message to tell people to wear masks all the time.

but here's some additional intuition:

1. it's true that virus particles are roughly the same size as smoke particles, but infected people exhale virus "pucks" that are agglomerations of multiple viruses and water, leading them to fall while smoke floats (giving us the 3-6 foot rule, per prior coronavirus studies).

2. a single virus particle in the air without water could float around but is overwhelmingly likely to fall apart quickly. the air doesn't provide the countervailing forces to keep it together, and the bombardment of energies from all around also pull it apart.

3. the fact that a homemade mask allows smoke right through but filters out some portion of the virus pucks (as per your prior link) is evidence in itself of the differential affinities of smoke and virus pucks.

but let's face it, most people wearing masks (outside) do it because they think it's protecting them from the filthy other people. however, if you're sick, all you're doing is concentrating the virus pucks in one place right in front of a face we'll each touch 30 times an hour. no lay person consistently observes the contamination rules that hospital personnel do, especially when infection rates are <0.1% and failure to do so has no obvious downsides. masks could in fact be more dangerous because of a false sense of security.