[samatman]

Alright, that's a decent point. KN94 is cloth, after all, and it's what I use. I was using "cloth mask" colloquially to refer to the masks made of ordinary cloth which have become pretty much standard uniform in the parts of the US with mask mandates. You can do a little better with multiple layers and tighter weaves, but, not much. If it's not specifically designed to filter particles as small as aerosols, it won't, and if it doesn't have a number after its name, it isn't so designed.

I don't think it's accurate to say that those are better than nothing. The false sense of security could easily lead to people staying longer indoors, or entering indoor spaces which they would consider dangerous if they didn't have the misconception that cloth masks protect them. It's a very small amount of protection, so it doesn't take much moral hazard to overwhelm it.

Could you maybe get a little less sick, if say 10% less viral aerosols passed through the mask? Ok, if I'm going to be very generous, sure. At the margins, someone is going to inhale a sub-infectious dose of aerosol who would have gotten a just-barely-infectious aerosol dose.

But this is like talking about condoms with holes in them. Most of the semen would stay in! It's not as pregnancy inducing as going bare! But I wouldn't call it birth control either.