[skat20phys]

My sense of the literature is that it's accurate in the limited sense that masks often don't have statistically significant effects in studies. It's maybe also accurate in the sense that the effects of masks are really being overrated, even many n95 masks.

However, in many studies there's a consistent trend toward masks doing something, in the sense that measures of dispersion are attenuated with masks vs not.

This paper is pretty poor in that it commits the classic statistical blunder of equating multiple nonsignificant results with overall effect size. It's very hastily put together.

One of the meta-analyses cited is an example of some of these issues (Offeddu, V. et al. 2017). You can see there's few studies and the ones included result in a nonsignificant effect, but it's almost significant and in the intuitively expected direction (PPE having an effect). But then there's issue of publication biases etc.

My general impression is that the truth is somewhere in between, maybe closer to what this essay is arguing in the sense that masks are much less effective than people think, but probably not actually technically correct in that masks probably have some effect.