Our district just started using gradebook on skyward (online). Now that we enter all of our grades online, there is no room for comments. I teach kindergarten, so I strive to make things as positive as possible when communicating with parents. I created this form that lets parents know my general thoughts on their child's progress, what I'm most proud of them for, and areas of concern (if there are any.)
I've found that parents appreciate this almost more than a report card with numbers all over it. I hope you get the same response!