I can’t really imagine a mechanism by which a mask would still let the same cloud of particles from a cough disperse in exactly the same way, but uniformly remo

I can’t really imagine a mechanism by which a mask would still let the same cloud of particles from a cough disperse in exactly the same way, but uniformly remove 70% of them. Surely if it is blocking that many particles it’s also disrupting the spread of the remaining particles. Or it could very well be the opposite of what you’re saying, maybe blocking that 70% of particles is enough to stop even more than 70% of the transmission opportunities. That wouldn’t be crazy if the spread is mostly via large droplets (most likely to get stopped by a mask) rather than aerosolized particles, which has been suggested. I think your argument is that it’s just not scientifically proven, but we have to make decisions today with the best information we have. Wearing masks still appears to be a good idea, has very low cost, and has been shown to help for a long time for all kinds of respiratory diseases.