Hearing Downes talk about cohorts was quite illuminating, in this context. The course is a kind of time-limited community of experience. It specifically excludes any Community of Practice, but that’s all fine.
In anthro, we encounter the notion of age-sets, which are actually quite similar to cohorts (typically made of people who are initiated at the same time). My friends in Mali would talk about their «promotionneurs» in both school and social contexts. In their case, the community of experience did lead to Communities of Practice, with a longterm sense of belonging and interdependency.
So a “course” (as in “MOOC”) is something of a pretext. But, as with most social constructs, it remains useful when we don’t restrict ourselves to it.