I would love to see a solution for this in the browser. If there was a tag, or some metadata attribute that indicated where each part of the document originally came from, you could just configure your browser to not render parts you don't trust. So in this case, YouTube could just flag the comment section as being provided by other users, and you can choose to block it if you don't trust other users to provide appropriate content. I would love to say that websites would flag ads as coming from a 3rd party ad company, and we could choose to block those too, but of course they wouldn't.
