I'm really liking the Marking Guide comment feature. Before, I was storing frequent comments in a Google doc and cutting and pasting, but now all my frequent comments are right there in the assignment grading window itself. Very slick, and a big time saver.
I'm was thinking that it would be fantastic if the same frequent comment feature were available with rubric grading as well. There are assignments that I want to keep as rubrics, and yet I often find myself making the same comments to students in the comments sections of those assignments. If I could select comments to apply in rubric gradings comments just as I can with comments when I use a Marking Guide, it would make using rubrics even easier.