> I am broadly anti-Worldcoin but it is reasonably competently executed at a technical level. It would be good to understand what they actually did before declaring it to be impossible.

+1 to this. I'm very skeptical of the project (even though I know some of the people working on it), but the problem space is extremely hard and they're giving it an actual shot. If you can think of a potential problem in 5 minutes, I guarantee you that they've thought of it too.