All comments should be entered under Attendance in the grade book rather then any of the other subject areas like Math, Reading, etc. in the following steps.

  1. Access Score Inspector via Final Grade area by right-clicking and enter your "global" or general comments that apply to all students for the first student.
  2. Then right click again and select Fill Scores and choose to fill comments for all the students.
  3. Then access Score Inspector again and add individual comments for each student. 
  4. Save frequently

This should all be done in Attendance. There is no need to add comments in the other subject areas and it will soon get confusing which areas have which comments.