Administrators can post comments in the Comments Tab of a Change Request, regardless of having a role in the Change Request or not.
Managers and Regular Users
Comments can be posted by Managers/Regular Users who have a role in the Change Request such as Creator, Approver, Responsible Person, or QA.
Managers/Regular Users who only have a role in the Change Request as Responsible User for a Task will not be able to post comments.
Read-Only Users cannot post comments.