All users that have access to a file or folder (via native rights or shared) can read the comments on that file or folder.
All users, except public users, can write comments.
Comment writing for public users is configurable, but it is off by default for two reasons:
Because public users are anonymous, there is a risk that they might be abusive, offensive, or meddlesome.
Micro Focus plans to add more granular control over who can see comments in the future:
Add private comments that are directed at a specific set of users or groups. (In addition to open comments that are visible to all users with access.)
External users cannot write comments; they can only view comments.
Public users cannot read any comments.