This idea immediately clicked in me, and my first thought was: "Why not make it so others can see your notes as well?". And soon it transformed into something much more complex where users could not only write notes, but also interact directly with other users of the extension through chat, gis, and cursors!
It took me a few weeks, but I was able to read through docs, work on the extension itself (content script and service worker), socket.io, node, build up a website, publish it in the Chrome store.
I've introduced it to my coworkers and a few other devs, and so far, each one of them came up with a different usage for the extension, but loved the idea of adding a social aspect to browsing.
I thought it would be great sharing it with everyone around here and gather feedback from the HN crowd!