If your instructor has assigned groups, when inside an assignment, you'll see a group icon in the toolbar on the right side:
If you are the first one in your group to comment on a particular document, then you won't see any other comments in the document, (even though other students in the class may have also started commenting). This is normal; All conversations
If you consistently aren't seeing many comments, you may want to ask your instructor about the group size for the course (they may decide to make the groups larger).
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