When teachers have their grade book “Format” (see “Setup > Classes/Subjects”) set to “Elementary core”, then students get ONE comment per term.
When the Format is set to “Middle/high school…”, then students get one comment per CLASS per term.
For the former (“elementary core” format), the teacher might enter the comment in any class, but the comment is attached (database-wise) to the student.
(Note that it is totally fine in Jupiter to set that “Format” to “Middle/high”, even for elementary students, so that teachers can enter subject-specific comments. That setting doesn’t affect anything else.)