#40031 (Consider Adding Web Annotations to WordPress) – WordPress Trac https://core.trac.wordpress.org/ticket/40031#comment:5
Mostly to provide some additional resources to the conversation I'll add the following:
Web Annotation Working Group's [https://www.w3.org/blog/news/archives/6156 three recommendations and two additional notes]
Prior to the WPTavern post which motivated the conversation, there was a [https://hypothes.is/blog/annotation-is-now-a-web-standard/ post written by Dan Whaley of Hypothes.is] who worked extensively within the group. This post has some interesting overview, but those interested in a fully implemented annotation platform (presumably using many of the pieces of the proposed standard) should take a quick look at [https://hypothes.is/ Hypothes.is], what it is and what it allows. Their front page has a pretty useful video introduction.
Keep in mind that some of the standard is geared specifically toward browsers and browser vendors, though WordPress could certainly implement some of the pieces from the CMS side.