Microsoft’s partner portal website mysteriously said his account had been deactivated, without specifying why.

My money is on Microsoft's AI based detections causing false positives again. I spend way too much time chasing ghosts from Defender. Their machine learning based signatures are especially egregious. You get an alert with a name like "Win32/Wacatac.b!ml". That last "ml" bit denotes that it's machine learning based. And then you get fuck all to help you determine why the alert fired. Sure, it might actually be a trojan. More likely, it's a false positive. But who knows, because Microsoft won't provide enough information to perform a reasonable analysis of the binary.

And MS has been pushing CoPilot hard. It's in everything and it's happy to slop up answers for you. The accuracy of those answers though can be a bit spotty. I'd certainly never turn it loose on tools which can have business impact. But, I doubt Microsoft has any such reservations about letting CoPilot slop all over third party devs.