The main puzzling part is why there isn't a single edX site where each course is a separate tag.
This would allow edX students to cross-pollinate knowledge, handle "edX meta" questions in a single place, keep more transient information like course deadlines or whatnot off Stack Exchange where it doesn't belong and generally have a single, larger, more lively, more healthy, better moderated site. It would also scale better and avoid graveyardsgraveyards.
From a distance all you'd really need or want is making the course tags (like cs50 or cs169 and a catch-all edx tag) mandatory, so that each tutor still has a view on "their slice" of the site.