I think most people, and definitely myself, when they sign up to be an organ donor, they think of the liver, kidney, and heart. Things that will help other people.

Not the brain, the center of conscience, being kept in some sort of horror-movie half-alive state. I do not think we understand consciousness enough to rule out what those brains are experiencing.

That's fair. Personally I wouldn't mind, but when you put it that way it makes sense people would be wary. Kind of reminds me of the series Pantheon, which is amazing but also kinda disturbing for similar reasons.

> half-alive state

The brain can't be "half-alive" after you've died.