Any reader can add a comment to any page or media file of a book without having to register first by clicking the link at the bottom of the page. Comments, however, are moderated, and will not become visible on the site until an Author User for the book author explicitly makes them live. To check whether your book has comments awaiting moderation, click "Dashboard" in the top-right corner. If the "Comments" tab contains a red badge, that number inside indicates the amount of comments which are not currently live. Click the tab to see the comments; you can click on the URI for each one to read it in its entirety. You can make a comment live either by clicking the "Make Visible" button at the bottom of the comment's page, or by clicking the "Edit" button for the comment in the Comments tab, setting "Live?" to True, and clicking Save.