Given the quality of the forums included in the LMSes I’ve had the misfortune to be exposed to over the years, Discourse would be an intergalactic leap forward in user experience.
We’ve got plenty of educational institutions amongst our hosted customer base, although I don’t see any obviously listed on our customers page. I’d be surprised if some of them weren’t using Discourse as a course discussion system. Hopefully one or more admins from those sites hang around here and can add their thoughts.