That's science fiction, though. The Everettian Many Worlds Interpretation is just that: An interpretation of a set of equations. And pretty much by definition the worlds cannot interact in any way. Even if there were some obscure way to differentiate between MWI and, say, the Copenhagen interpretation, I wouldn't expect it to become feasible anytime soon. But as far as I know there cannot be any experiments differentiating between the two (or other interpretations), because they're simply different interpretations of the same equations. They predict the same experimental outcomes.

Why should I check it out? Is it illuminating, or just a good story, or what?

Sorry I didn’t clarify. It is fiction, but I think it describes a plausible reaction of the general public (the layman of the comment I replied to) to this hypothesis if it was discovered to be true. Don’t want to spoil the good part of the story beyond that!

Ok, and appreciated! Will dig it up, thanks.

Literally everything written by Ted Chiang is worth reading because he is a hell of a story teller.