The deepfakes that people are worried about are ones that, if they were real, they'd not authorize anyway, so the lack of a digital signature wouldn't help dist

The deepfakes that people are worried about are ones that, if they were real, they'd not authorize anyway, so the lack of a digital signature wouldn't help distinguish deepfakes from leaks. At the same time, digitally signing something real just makes it hard to disavow later when you suddenly feel embarrassed by it. Hence there's little reason to sign anything. On the other hand, maintaining a list of photos that are allowed to be posted, where platforms take down anything else with a facial recognition match might work better than the status quo where platforms maintain lists of stuff that isn't allowed to be posted. But it's up to platforms whether they want to implement such a system.