There is a mention of something that might be what Yudkowsky is on about in this Wired story:

The group had become especially fixated on a particular rumor, namely that the nonprofit MIRI had potentially used donor money to pay off a former staffer. The ex-employee had launched a website accusing MIRI leaders of statutory rape and a coverup. Though the facts were never litigated in a courtroom, MIRI’s president wrote in 2019 that he had checked “some of the most serious allegations” and “found them to be straightforwardly false.” The website’s owner had agreed to retract the claims and take the site down, the president said, under conditions that were confidential. But what angered LaSota and Danielson was as much the idea—in their minds at least—that the nonprofit had succumbed to blackmail as the allegations themselves. In negotiating, they believed, the organization had violated one of its fundamental principles: “timeless decision theory,” a concept developed by MIRI cofounder Eliezer Yudkowsky. (Yudkowsky, who later renamed it “functional decision theory,” declined to comment for this story.)

This article doesn’t make it sound so much like a “FOUNDING BELIEF”; lots of weird shit like the brain hemispheres business appears to have come first. But the much more interesting thing is at the end of the story:

One of the last things LaSota seems to have written for public consumption was a comment she left on her own blog in July 2022, one month before she supposedly went overboard in San Francisco Bay. “Statists come threaten me to snitch whatever info I have on their latest missing persons,” she wrote, seemingly referring to deaths by suicide that had already happened among those who’d embraced her ideas. “Did I strike them down in a horrific act of bloody vengeance? Did I drive them to suicide by whistling komm susser tod?”—a German phrase that translates as “come, sweet death.” “Maybe they died in a series of experimental brain surgeries that I performed without anesthetic since that’s against my religion, in an improvised medical facility?”

Below it was pasted a stock photo of two people wearing shirts that read, “I can neither confirm nor deny.”

(Archive link to Ziz’s blog)

Hmm. Hm-hmmm.