Scott Aaronson was already reading along to it as it was published. If we paid David Deutsch to read it, I expect him to just say, "Yeah, that's all basically correct" which wouldn't be very in-depth.

From those who already disagree with MWI, I would expect more in the way of awful amateur epistemology delivered with great confidence. Then those who already had their trust in a sane world broken will nod and say "I expected no better." Others will say, "How can you possibly disregard the word of so great a physicist? Perhaps he knows something you don't!" - though they will not be able to formalize the awful amateur epistemology - and nod among themselves about how Yudkowsky failed to anticipate that so strong a reply might be made (it should be presumed to be a very strong reply since a great physicist made it, even if they can't 100% follow themselves why it is a great refutation, or would not have believed the same words so much from a street performer). And so both will emerge strengthened in their prior beliefs, which isn't much of a test.