I've learned that asynchronous communication is the "heart" of online learning and that synchronous communication, a.k.a. "chat sessions" have four major disadvantages, and is best used for 1:1 clarifications personal advice. Video-enabled chat tools increase the effectiveness of synchronous small groups. I've also learned to promote interaction by responding to groups of related responses rather than individual messages, and encouraging learners to comment on a selected learner's response.
