As of this morning, when you open a new Google doc, you will have a new discussion feature. Docs have always had a commenting feature, but this discussion threads down the side of the page in the margin. You can direct comments at a specific person by putting at @name in front of the comments. You also subscribe to follow-ups via e-mail.
I think all this is good news for teachers. We’ve always been able to comment and give feedback to students, but this really enhances the peer review process.
Check out this fast but clear video: