Navigate to the Test Coverage primary tab and then to the Builds secondary tab. In the specific build's details window, click on the comments icon in the right side vertical panel to expand and view the comments section. Click the icon again to hide the comments section.
Users will need view permissions in the test coverage module to view build comments. Depending on the settings of a users project permissions, users may be able to view all project builds or just a subset of them. Project owners manage the permissions for project members.