When a discussion thread has many posts, it is beneficial to collapse the replies to see the main posts. When collapsed, each top-level post will show the number of replies and indicate the number of replies, and if there are any unread replies. This is an easy way to view the discussion thread. While there is a button at the top of each discussion thread that will collapse replies, and another button to expand all replies, the default when entering the discussion thread is that all replies are expanded. However, when selecting the collapse replies button it will change the view at that time, but when returning to the discussion, this is not saved as the default behavior. The default always seems to be set to expanded replies. So a student, or instructor, would need to choose the Collapse Replies button every time upon entering the discussion to merely see the top-level discussions. There does not seem to be a way to save collapsed replies as the default behavior.