On upgrade from 1.6.3 to 1.7+, legacy course creators are being listed as teachers in each course on site pages. This can be confusing. In 1.6.3, course creators were teachers who were allowed the additional authority to create (usually their own) courses. But they were not teachers of all courses. On upgrade, I would not have course creators be listed in this way.
A workaround is to remove these as creators, and create a new role that has the authority one wants to give for this position. But, in my view, such users should not be listed as teachers of each course.