Any group reading of a document hits the same wall: who is highlighting what. One reader chases the thesis, another hunts contradictions, a third collects terminology — and they all edit the same page.
Color-coded annotation tied to a legend makes everyone's reasoning visible without turning the margins into a wall of comments. You see at a glance: the team agreed here, Lisa raised a question there.
Days later you can reconstruct how the team actually read the material — without spelunking through chat threads or guessing what "agreed" really meant.