I really would have loved this as it seems so well put together, clean, and thought out except for on flaw. Yes, it does create notes for a page, however those notes do not show up on the page at all. In fact there is nothing to let make you aware that you ever did create a note on a page. Instead you have to click on the extension and then you will see your note. So, unless you remember you've made a notation to a page somewhere, or refer to notes made in the past within the extension itself and then revisit a page from there, you have no idea if you've done so. Its a bit unrealistic to expect people to remember they've created notes on websites/pages should they go back to them if there is no visible sign that you've done ever done so.

Aside from that major flaw, the only other aspect I would add would be to allow for the add-on to be accessed through the contextual menu rather than having to click on a pinned icon in the toolbar.