First, this is what the blog SHOULD look like, with your initial topic as a new post, and the Cornerstone students responding properly as a comment:
However, often they will add a new post, rather than a comment, and it will get confusing. Only you, as Capstone students, should be adding new posts.
So you will have to remove their post, and add it back in as a comment in order to keep the blog "clean." First, copy their post and add it in below the original topic that it relates to as a comment (they typically do this with the introduction posts). Add some context, so that they know what's happened to their post, such as "added to the comments section for Jane Doe by Jane Moody."
There is an option in the dashboard to "edit posts." In that option you can delete a post:
Then your blog should be ready for your next topic. And MUCH easier for the Cornerstone professor to grade!