Apologies for jumping in late.
I think for the On-demand course linking, as @irreverance suggests a link beneath the video, or at the end of the intro/heading text, would work well. Just being clear to people to point out which course/module they're commenting about.
In an ideal world then you're right @HAWK , a discussion group for each course, or module or however granular you want to get would work, but for an online course I think it's safe to be fairly general. Perhaps a high level group for each of the three different courses would work?
How do you handle this for the more in-depth "classroom" course that you guys run? This would be a good opportunity to have a closed group for each intake/class, for them to discuss concepts before, during and after their particular session, which is a way I've done in the past for classroom type learning.