In 1.7, anyone with moodle/course:update capability would show up on the course description area. To help with this problem we added 2 extra features in 1.8.
1) Assignment could be hidden. This prevents users with this hidden assignment showing up at the course participants page and on the course description area for users without the capability to view hidden assignments.
2) There is now a new global setting under appearance to determine what roles is displayed on the course description area. The order of the roles displayed is the same as the sort order of your roles (customizable). This setting is default to "Teacher".