The comment system is very good, keeping in preferemce to disqus.
Anyway, if you reply to a comment and then cancel and then hide comments, the comment form is also hidden.
I'm not entirely sure that this is the intended behaviour, changing the replyToComment function in blog.js as follows, puts the comment form back where it started instead of appending it to the comment list.
Change from: base.appendChild(commentForm);
To: base.parentNode.insertBefore(commentForm, base.nextSibling);
In case anyone is interested.