This idea has been developed and deployed to Canvas
I think something changed this last weekend when my school updated Canvas. I can no longer drag around the comment box when I'm giving feedback in the grading rubric. Thus, the box blocks my view of what the student has written, making me copy/close/read/reopen/paste my words when I need to scroll down the page. Note that the comment box doesn't have the ability to be resized, nor dragged across the page.