Yudkowsky has declared the many worlds interpretation of quantum physics is correct, despite the lack of testable predictions differing from the Copenhagen interpretation, and despite admittedly not being a physicist.
I think there is a fair chance the many world's interpretation is wrong but anyone who criticizes it by defending the Copenhagen 'interpretation' has no idea what they're talking about.
If you know more Eliezer Yudkowsky facts, post them in the comments.