I think that the course was referring more to discussion rather than teaching in general. The idea that the chat structure can make ongoing discussion challenging is not really off-base either, as the the IM feature can quickly become overwrought and difficult to follow. For one word responses, yes/no questions, and show of "hands" I think it functions well, but to have a full blown dialog among multiple students that way and trying to follow it is a bit like herding typographic cats.
Now, that said, the chats are invaluable for demos, Q&A, slide lectures, etc... I am as surprised how few students attend the chats as the rest of you seem to be, they miss so much when they don't attend!
