Sidebar vanishes after comment is posted

The sidebar shows up on the main page and in single posts that have no comments. But when a comment is posted, the sidebar vanishes from single posts. (Also, the comments don’t seem to be visible.)

How can I get the sidebar to stop vanishing?

The blog is at burneylawfirm.com/blog. Using the ‘minimalism’ theme. Only have version 2.3.3 because that’s all Yahoo! allows, for some reason.