I've been wondering for a little while why the comment box wasn't appearing at the bottom of each post. It turns out Cusdis, the plugin I use for comments, is no more, discontinued by its developer and now unavailable.
So a replacement was needed, and that replacement is CommentBox. The only down side to CommentBox appears to be that you still need to log in even to leave anonymous messages, which is a real shame as having to sign up will no doubt put some people off leaving a comment.
Not that anyone is commenting anyway, but it's nice for people to have the option!