Adding premises like "Odin created everything" makes a theory less probable and also happens to make it longer; this is the entire reason why we intuitively agree with Occam's Razor in penalizing longer theories. Unfortunately, this answer seems to be based on a concept of "truth" granted from above - but what do differing degrees of truth actually mean, when two theories make exactly the same predictions?

and

Imagine you have the option to put a human being in a sealed box where they will be tortured for 50 years and then incinerated. No observational evidence will ever leave the box... Now consider the following physical theory: as soon as you seal the box, our laws of physics will make a localized exception and the human will spontaneously vanish. This theory makes exactly the same observational predictions as your current best theory of physics, so it lies in the same equivalence class and you should give them the same credence.

Why do we only care about observational predictions and not all "in principle" predictions? (Serious question, not rhetorical). My intuition is that in the first quote "Physics" and "Odin created physics" aren't in the same equivalence class because the latter makes an additional prediction: the existence of Odin. Similarly in the second quote, there are differing predictions about what is happening inside the box even if they are physically impossible to test, so I would put the two theories in different equivalence classes. I would do the same for MWI and Copenhagen quantum mechanics.

This is pure intuition on my part. I haven't had a chance to take a look at the math of K-complexity and the like, so I might just be missing something relatively basic.