https://www.simplecommenter.com/
https://gist.github.com/crodas/2df77bc80ab675ad3224cfe9371e4af5
A block-style editor with clean JSON output
https://github.com/editor-js/awesome-editorjs
Inline Comments adds your comment system to the side of paragraphs and other sections of your post. WordPress plugin.
:bulb: dokieli is a clientside editor for decentralised article publishing, annotations and social interactions
A JavaScript library for text annotation