@evmar Good catch, thanks. I have a fix up (rolling in some other changes) here: https://github.com/linebender/linebender.github.io/pull/44
Also, I should link to discussion on the Zulip: https://xi.zulipchat.com/#narrow/stream/260979-kurbo/topic/Power.20law.20spirals.20and.20their.20evolutes. That's got some more discussion, including other examples that suggest a power law relation, and a link to a paper by Gravesen which may contain a clue.
@raph TeX inline with your markdown seems like a lovely way to publish!