Very cool! I wish more editors would exist as web services, easily solving the cross-platformity that way.

This isn't a web service. It's a browser-based tool that runs entirely on your device. It's published as a static site on GitHub Pages, and ("but"?) everything it's doing is all happening fully in-browser.

I'm in the opposite camp. Give me some local tool that does disappear when the maintainer moves to the next thing.

Well and I can eat the cake as well, make it some native app that has proper performance.