At the moment a teacher (or other role with suitable capability) can throw themselves out of a course by clicking the 'eye' symbol on the enrolment plugin (Course settings > Users > Enrolment methods) that they themselves are enrolled by.

Example, teacher is added to a course using manual enrolment. They then look at the enrolment methods page and wonder what the eye next to manual enrolment does. If they click it they are unable to access this course.

The should be prevented from doing this. There's no possible reason (I can think of) for being able to do this.