Like "who watches the watchers".
Two kinds of workarounds come into my mind:
- Administrators and teachers have two user accounts. One standard account to take courses and obtain certificates (like normal students) and an additional account for their admin- and teacher-functions.
- Teachers get an extra course (or set of courses) where they only have the role of a normal student. This works only with teachers, and only if the teacher-role is defined on a course level and not as a global role.
Usually, teachers are supposed to have the knowledge by definition. They are the ones who create the questions and quizzes, so why should they need a certificate?
A professor does not take his own exam, he grades it. Why should he grade himself?