[jeffreyH (OP)]

See https://en.m.wikipedia.org/wiki/Quantum_Bayesianism
Does this clear up the mysticism of many-worlds and other such interpretations?

[chris]

I don't even know what that is!

[yor_on]

Interesting Jeffrey, and close to my views too. Although it may define it differently by ones presumed participation influencing it by expectations. But the origin seems to be the same, the one where you want to get out from the 'many worlds' theory's in where everything, and at all times, bifurcate or split ad infinitum.

[yor_on]

You can compare it to this. https://www.thoughtco.com/many-worlds-interpretation-of-quantum-physics-2699358

[Colin2B]

Does this clear up the mysticism of many-worlds and other such interpretations?

I'm used to using with x & y coordinates (imagine a slice through the sphere) to describe probabilities of electron & photon spin eg in entanglement and polarisation, and obviously you can use the full 3D to describe all quantum states, so yes it does have something useful to say, but I don't think it clears up many-worlds.
I would view many worlds as a way of handling the probabilities rather than an interpretation which says the worlds have a separate reality, but that's just my interpretation