Rolf, surely the simplicity of MWI relative to objective collapse is strong evidence that when we have a better technical understanding of decoherence it will be compatible with MWI?

What do you mean by "compatible"? Do you mean, the observed macroscopic world will emerge as "the most likely result" from MWI, instead of some other macroscopic world where objects decohere on alternate Thursdays, or whenever a proton passes by, or stay a homogeneous soup forever? That's a *lot* of algorithmic bits that I have to penalize MWI for, given that this has not been demonstrated.

Here's the linchpin of my argument: why should I believe, a priori, that the observed macroscopic world has a decent chance of popping naturally out of MWI, any more than I should believe that the observed world might pop out from the philosophy "All Is Fire?" Should I believe this just because some people have convinced themselves that it probably does (even if they consistently fail to demonstrate it in a rigorous way?) But such post-hoc intuitive beliefs are notoriously unreliable. Extreme example: many people believe that quantum mechanics emerges naturally from Buddhist beliefs (yet, again, oddly they cannot demonstrate this in a rigorous way, and as an added coincidence, they only started saying this *after* quantum mechanics had already been discovered by secular experimentation.)

Aside: if MWI'ers had *started* in 1890, and then used their "simple MWI" theory to go *backwards* from macroscopic observations to infer the possible existence of quantum mechanics by asking themselves "from what sets of simple theories might the macroscopic world naturally and intuitively emerge", now *that* would have impressed me.