And here I try to make some criticism of the posted work, and constructively. I think coding defensively for the noscript case is a good, important practise, even if the chosen remedy is to show up a "please enable JS" message. And then there's the case of printing the page, the read-it-later things, archival, etc... I can't run JS on paper, or on PDFs, right? But the WWW is ephemeral, and if something is important, I have to archive. And people have disablities, how would margin notes be readable with say 5x zoom? How will a disabled person get to read the popup margin note if he can't even move the mouse to hover the anchor tag? One may well say that disabled people are not worthy of seeing their content, and however disgusting may it sound they've the right to say so, but the OP may be open to such suggestions for inclusivity and improvement, and I suggest.
I think the JS CDNs are the most stupid things on the world. It is a virus vector. Hack one CDN, and you'll get to run your code on maybe millions of websites. And who decides which CDNs are major, and/or better or more secure?