Eliezer: I'm not sure you'd really get much interference effects between indistinguishable hubble volumes.

What I mean is you'd need some event that has in its causal history stuff from two "equivalent" hubble volumes, right?

Otherwise, well, how would any nontrivial interference effects related to the indistinguishability between multiple hubble volumes manifest? Configuration space isn't over the hubble volumes but over the entirety of the universe, right?