I like this. Building on your idea with the yellow colour code, I think it would be good to have functionality to mark typos, with the option of providing a revision suggestion that the author can press accept or reject on. Similar to how edit suggestions work in Google Docs.
In-line commenting.
Invisible by default so they don’t distract, but you can easily switch visibility.
So the reader particularly interested in some section could dive into the comments particularly about that section.
Also, as a further feature, you could color code different comment types, like:
blue (default): just a comment
yellow: fix suggestion
brown: link to previous discussion / relevant resources
red: critique ?
Also see @Emrik’s comment with more rationale.
I like this. Building on your idea with the yellow colour code, I think it would be good to have functionality to mark typos, with the option of providing a revision suggestion that the author can press accept or reject on. Similar to how edit suggestions work in Google Docs.