Be careful with this plugin on newer versions of WordPress >4.7 as the shortcode was throwing a fatal error on pages on which it appeared.
Kris Shaffer, the plugin’s author
Web annotation seems to promote more critical thinking and collaboration but it’s doubtful that it would ever fully replace commenting systems.
But why not mix annotations and comments together the way some in the IndieWeb have done?! A few people are using the new W3C recommendation spec for Webmention along with fragmentions to send a version of comments-marginalia-annotations to sites that accept them and have the ability to display them!
A good example of this is Kartik Prabhu’s website which does this somewhat like Medium does. One can write their response to a sub-section of his post on their own website, and using webmention (yes, there’s a WordPress plugin for that) send him the response. It then shows up on his site as a quote bubble next to the appropriate section which can then be opened and viewed by future readers.
For those interested, Kartik has open sourced some of the code to help accomplish this.
While annotation systems have the ability to overlay one’s site, there’s certainly room for serious abuse as a result. (See an example at https://indieweb.org/annotation#Criticism.) It would be nice if annotation systems were required to use something like webmentions (or even older trackback/pingbacks) to indicate that a site had been mentioned elsewhere, this way, even if the publisher wasn’t responsible for moderating the resulting comments, they could at least be aware of possible attacks on their work/site/page. #