Monist vs. Dualist Experiment?

[genkaus]

My acceptance matters precisely because my complicity (or that of anyone else) is required in order for your evidence to be presented as valid.

Wrong again. The validity of evidence is not determined by consensus but by logic. The consensus is a tool to minimize errors in logic.

Your scientific hypothesis is a false syllogism: "I know this wagging tail to be caused by a dog, therefore all wagging tails are evidence of a dog."

If dogs were the only known cause of wagging tails, this hypothesis would be a valid one.

A more correct analogy would be: "All the known instances of wagging tails are caused by animals, so any wagging tail can be regarded as prima-facie evidence of existence of an animal".

It's true that dogs can have wagging tails. But this does not make a wagging tail adequate (or very meaningful) evidence of a dog.

That's because we already have evidence of other animals having wagging tails. The inadequacy of evidence in this case is the reasult of known and proven alternate possibilities.

The correct analogy here would be: All the known instances of wagging tails require an animal wagging it. Which is what makes a wagging tail an adequate and meaningful evidence for an animal.

If I choose to ACCEPT this flimsy evidence, it's an arbitrary choice, not a rational conclusion.

Exactly - if YOU choose to accept it. Acceptance of evidence on those terms is meaningless, which is why your acceptance is irrelevant.

And my willingness to believe that any particular physical structure really experiences qualia is based purely on a hunch, as necessarily is yours or anyone else's. No science, here-- only some hunches with a sciencey hat on and some minus that unnecessary frill.

That's where you are wrong. As demonstrated earlier with the inconsistent application of your agnosticism, while your acceptance might be based on a hunch, others adhere to a higher standard.