The best footnotes I've found provide nice bidirectional linking for easily jumping to / back from the footnote so that it disrupts the reading as little as possible.

The beautiful / fun part about having a blog is that it's your own little garden: you can adjust things just like how you see fit, and footnotes were just a case where I figured I'd do without until I could implement it in a way I was happy with.

Have you considered the very low-tech solution of simple HTML anchors to link back and forth?

Definitely! That's what my goal implementation will be compiled to, anyway. I use Hugo, a Go static site generator, to build the markdown posts into the site. Adding footnotes is just a matter of figuring out how to use the right syntax in the markdown, output the right anchors in the HTML, then sprinkling a little CSS on top.

I'm 99% sure Hugo can do this, I've just learned to be wary of putting things in between myself and actually hitting the damn publish button.

Hugo Markdown guide says yes: https://www.markdownguide.org/tools/hugo/

With link to syntax: https://www.markdownguide.org/extended-syntax/#footnotes

May I suggest you add "footnotes on hover"? I feel like this is the ultimate expression of the idea, and books would do it that way if they could.

Hover is a great experience on desktop, but it annoyingly requires having a separate solution for mobile. Right now 60+% of the traffic on the site is from mobile devices, so figuring out something (hopefully simple and very lightweight) that works for both mobile and desktop is the goal.

Your suggestion is noted, though!

Along these lines, I've always liked the system Randall uses for What If: https://what-if.xkcd.com/

Agreed. I've pinched his popup implementation for my homepage and expanded it a little so that there's both a footnotes section with anchor links at the bottom for non-JS use and search engines, as well as the popup panels. E.g. https://www.buttercookie.de/The%20Burkiss%20Way/Transcripts/...

Oh thanks, I really like this variant. It needs a name: click-to-hover, perhaps?