Comment Templates can contain different items for different types of user groups (Business, IT). To ensure that certain Comment Template items are editable only by certain users you can assign Comment Template items to roles.
The pre-condition to assign Comment Template items to a role is to define roles in the "User and Roles Management" area where you can also assign users to a role.

The following sample will clarify the required steps: 

The Template item "Business Aspects" of the CompositeProvider Comment Template should be editable only by users that are assigned to the role "User".

When a role is assigned to a Comment Template item, only users assigned to this role will be able to edit this item. Users having a role that is not assigned to the Comment Template item can only view the content, but they are not allowed for editing.