Carnival is an unobtrusive, developer-friendly way to add comments to any web site. Installation is easy. Once you’ve created a Site , just add a piece of HTML snippet to the bottom of your page, and then you are done.
By default, a hidden sidebar will be added to any article elements. Within these elements, each p and pre element will receive a small indicator, visible on hover. When clicked, the sidebar will expand, allowing visitors to comment on that specific portion of your article. Carnival also sends email notifications on replies and provides an RSS feed of recent comments on your Site.
Read more: https://carnivalapp.io/