I added a block for comments where I want my students to post, but not read. It's just a method of messaging me if they need to request a document. I limited permissions on reading comments to just teachers and managers (removing authenticated users, guests, and students). They can still see their comments and other user comments.
The permissions I revoked were under Front Page permissions and I filtered by comments. To ensure I was revoking the correct one, I revoked "post comments" (located right above "read comments") to authenticated users, guests, and students, and the ability to post was removed. So it is the correct category (Capability Course).