OK, so "there could be cases where it is rational to update." How would you do so?
(I can't understand what an update could reasonably change. You aren't going to make the probability of any particular side more than 1/6, so what is the new probability?)
I don't know either. I can make up a scenario, based on a series of die throws, history of win-losses and guesses based on that, but that would simply be conjecture, and still may not produce a reasonable process. However, this discussion reminded me of a scene in HPMOR. (The scene where HP's critic part judges that Miss Camblebunker was not a Doctor, but an actor. (After Bellatrix is broken out of prison.))
My claim is that you can't come up with such a conjecture where it makes sense to change the probability away from 1/6. That is why you should not update.
Another month, another rationality quotes thread. The rules are: