> It continues to amaze me how some of the smartest and technically savvy people on HN either do not recognize or refuse to admit how complicated a problem planet scale moderation is.

It's probably a variation of the trivial-core-problem [0]. When looked at roughly, it seems very easy; only when you start implementing it, you'll see all the edge cases appear. I made pretty similar points above to the ones you made - but on a quick napkin calculation, Retric's math checked out, to be fair. And when you're not in the business, missing the inherent complexity is easy.

[0] See https://blog.codinghorror.com/code-its-trivial/