"Jeffreyssai probably wouldn't give up against the Evil Barbarians if he were fighting alone."

WWJD, indeed.

But since Jeffreyssai is a fictional creation of Eliezer Yudkowsky, appealing to what we imagine he would do is nothing more than an appeal to Eliezer Yudkowsky's ideas, in the same way that trying to confirm a newspaper's claim by picking up another copy of the same edition is just appealing to the newspaper again.

How can we test the newspaper instead of appealing to it?