Academic Settings / Timetable / Timetable Settings / Visibility Settings & Rights / Show timetable comments on timetable views. Enable for the following user types
Setting -> Active -> Parent , Student , Teacher (Figure 1)
If a comment is created on a course in the timetable
Figure 1
Appears in the users’ timetable when the mouse cursor is over the course (Figure 2)
Figure 2
Setting -> Inactive
Comments are not shown to the student