Our teachers want to "moderate" discussions in a different way: they want the ability to mark, pin or feature correct or interesting comments so they are easily visible to all members of the discussion. A lot like how Community has the obvious "Solved! Go to Solution." near the top of the page, as well as the comment clearly marked with a green box. 

This is just as much a Q&A function as it is a "moderate" function and we think it is very useful. If someone has the answer to a question (or if the teacher or author wants to feature a good comment in the discussion), then it is much better for the teacher or author to be able to send students directly to the comment, rather than everyone having to scroll through all comments to find it (or the teacher/author having to write their own comment with the same information). That marked/pinned/featured comment should then be visible without requiring users to expand the thread.