[lepton]

While I am skeptical of the protection against being infected when wearing the masks, especially by the untrained, there are some weird definition things stated here.

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The masks are to prevent you from giving the disease to others, not so much to prevent them from giving the disease to you.

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Agreed and understood, hence my wording.

But again, look at the details of what the study purports to say.

[exDemMom]

But again, look at the details of what the study purports to say.

The studies are looking at real world reductions in transmission achieved by mask use. I interpret that as including mask use by both trained and untrained persons.

Efficacy is how well masks perform under ideal circumstances, i.e. a laboratory setting.

Effectiveness is how well they perform in actual use. At least one of the studies (printed in the MMWR) looked at effectiveness of mask use, and found it beneficial.