We are finding ourselves lacking feedback comments in the grade book for forum engagement. I've created a Moodle Tracker Ticket with a suggestion to include a general comments field that would link to the grade book like the assignment feedback comments box does. We also think that if an assignment or forum has advanced grading methods there should be contextual links back to the activity page that displays the criterion feedback to the students.
Please vote on and watch this issue if this impacts you as well.
https://tracker.moodle.org/browse/MDL-77615
