The commentor role is someone who is allowed to view and write comments even if this permissions have been disabled in the document.

Button

Joining Experience For Users

“Everyone can View Discussions and Comments ” have been turned off.

“Everyone can View Discussions and Comments” have been turned on but “Everyone can Write Discussions and Comments” has been turned off.

Document Access Panel

Commentor Tab

Grant Request Permissions

Pending Tab

When accessing the pending tab the administrators will be able to accept of deny the users who have requested member access. If they have been accepted they will be added to the list of members and if they have been denied the user will get an email notification notifying them of the denial to join as member.