Paragraph commenting, or annotations is not exactly new. Readers have been scribbling in the margins of books, magazines and uni assignments for years. The online world has been slow to adopt this approach which is perhaps why Medium caused a stir and no shortage of admiring looks when it went the annotation route. Well, admire forlornly no more because I'm going to show you how to add paragraph commenting to your WordPress site. There are existing annotation solutions for WordPress but they are generally theme dependent, or in the case of CommentPress actually provide a theme.
This has some great advice and code for potentially adding marginalia.