Medium.com and Quartz are both famous for their innovative ways of presenting content. Both use side comments in order to allow to comment individual paragraphs rather than whole articles.
A few days ago SideComments.js was released by Eric Anderson. It allows an easy integration of that commenting system.

If you want to use SideComments.js within your WordPress installation, follow these 3 simple steps:
1. Download the adaption for WordPress on Github by strategio: WP Side Comments (.zip).
2. Upload the plugin to your plugins folder and activate it.
3. Go to settings –> WPSC. There you have to include two CSS-Selectors, one for your content, one for your comments. For example, in order to make the plugin work with twentyfourteen you have to write:

Be aware that you need a . for a class, or a # for an ID. If you don’t use twentyfourteen you can find out your selectors with developer tools in your browser.
Every comment is a regular comment in the WordPress system and can be edited, reviewed etc. in the WordPress backend.
That’s it 🙂