I didn’t see case-control studies or cohort studies. You should link to those.

Before and after photos are prone to manipulation and bias
Take a photo with your jaw pulled back for the before and then one with your jaw projected forward for the after. Use better lighting for after. Even if the person is not consciously intending to, these are so easy to manipulate.

Maybe surgery was done in some of those photos and the poster is not being forthcoming about that, if they have something to sell.

The evidence for mewing just doesn’t seem to be there. You give a lot of theory and anecdote and before/after photos, which aren’t worth much. The main proper source I see you list is https://academic.oup.com/bioscience/article/70/9/759/5872832?login=false, which itself seems to admit that there’s a lack of evidence for it

Another cost with a failed moonshot is damage to reputation. If I think that there is a 5% chance of another pandemic in the next 10 years and I spend the next 5 years working to mitigate it, there is a 95% chance that everyone who tells me I am crazy will end up looking like they were right.

Interesting I wasn't aware that The Life You Can Save and Founder's Pledge had this fund going. Thanks. I don't have an an answer to your question.

Alternative response: If someone told me that there was somewhere between a 0.00001 and 0.5 chance that I was to be struck by lightning tomorrow, it would not be reasonable for me to say “well almost everywhere within that confidence interval I have a >1% chance of being hit by lightning tomorrow”

Almost everywhere within

Most of these CIs start at zero and they can't go below zero so shouldn't we consider these on a log scale? In which case the scale goes back to negative infinity and "almost everywhere within" is meaningless.
 

The Rethink Priorities Welfare Ranges have absurdly wide confidence intervals. So wide that I would argue they're almost worthless.