The idea is very similar, but I can't agree with a few implementation details: - The extension shouldn't need to have access to the page. Inserting an iframe into the page seems wrong. - The extension shouldn't own the comments. It should be a window to the comments, not a gatekeeper. It should be possible to implement alternative UIs and alternative extensions and connect them to the same comments. - The extension should allow to switch the UI and the data server.

I like the inline annotations, but likely it'll need full access to DOM.