My understanding is it gets the counts of dislikes from participating content creatos (the dislike count is still there, it’s just hidden except to the video authors) and for non-participating creators it uses data from the users with the extension. I think it applies some smart logic to predict the dislikes based on user feedback in that case, which may not be 100% accurate, but is likely at least somewhat close.
Despite Elon being insane, the idea of brain-computer interfaces could be really great. I’m thinking of people with disabilities or debilitating injuries. This could enable prosthetics with full dexterity that you can control. It could be life changing for some people.
I don’t know if that is the first thing Elon is aiming for, but any breakthroughs in the technology that could lead to it becoming a legitimate option to improve people’s lives, I think would be a good thing.