This is another question I had originally posted in the Q&A for the webinar but that there wasn't time to respond to. How much should instructors participate in online asynchronous discussions? Is there a sweet spot between posting enough to show that the instructor is engaged but not so much that they seem to dominate or control the discussion? I've read a review of the literature on online discussions that suggested they worked best when instructors posted occasionally to moderate the discussion—that is, they posted about how the discussion was going or on the nature of students' posts but did not weigh in on the topic itself. Thoughts?
I think the "sweet spot" begins in preparing the discussion with explicit guidelines on what to do, when, how, what kind of decision or solution or recommendation to reach, what evidence and/or reasoning to provide, and roles of group members.
After that, I think it's not so much the need for an instructor to post "occasionally" as to have a reason to do so that will encourage further discussion and acknowledge the relevance of students' thoughts. For example, an instructor might say something like "I noticed that you mentioned there is another way to view the problem. Can you give me an example of what you mean?" Or, perhaps "You explained how you would use the psychosocial model. I am wondering how might your analysis change if you used the wellness model."
These examples contain no evaluative judgment of the goodness or badness or correctness of student postings, but focus on extending their thinking. As you mentioned, it makes sense after "wait time"--after the students have had enough substantive contributions to a discussion for an instructor to see emerging themes--to bring together those themes in a micro-summary. When to summarize varies with how often the instructor requires discussions and the complexity of the content. If every week, maybe it's better to wait until the close of the time frame. But if a deep discussion every three weeks, then noting emerging themes can be helpful.
Of course, clarifying an explanation can be important at any time, as well as answering students' questions.
One other thought, if the instructor has assigned roles to members of a discussion group, and one of those roles is for a student to be the moderator, then how does the "moderator" role of the instructor change?
I'm a big fan of the online instructor joining in and expertly facilitating an asynchronous discussion, just the way we do when leading a discussion in person. Let's not shut down the students with critical replies or dominating contributions. And let's not ignore students -- we wouldn't when teaching in person, would we? Guide and facilitate a learning-centered conversation by, as you said, hitting the sweet spot in terms of the frequency and content of your posts. I've found it really helps keep students engaged. This can take practice, like when we first learned to lead a discussion in person, but it can certainly be done.