Ask HN: Comment tool for web pages, for collaborative editing?

I am looking for a js library that allows readers to add google doc / MS Word style comment bubbles to a sentence or word they highlight. It should work on any web page.

The closest I've found so far is annotator.js [0]. The problem is that, after adding a comment, the text is merely highlighted, and you have to mouse over it to view the comment again. In contrast, Google doc comments are always visible in the sidebar (unless you hide them).

Is there an open source js library that provides similar functionality?

[0] http://annotatorjs.org/