I've been called out previously here for having unknowingly introduced some undefined terms to readers, and which they found to be perplexing.
And I took that to heart, because I don't want my words to be perplexing. I instead want them to be clear and easily understood.
In my corner of the world, I haven't held a mimeographed document in my hands for ~35 years. I found it reasonable to assume that a non-zero amount of people here might find the term to be unfamiliar.
So I provided definition of the term on the basis that it may be unknown to some readers, and that more information is better than inadequate information.
In this instance I would have preferred to use hyperlinked text for visual brevity, but that's not a thing on HN. The normal and accepted style on HN consists instead of using footnotes.
And at this point, generating footnotes is nearly entirely muscle memory for me. So a footnote (with a URL) was included.
Thank you for your attention on this matter, fsckboy. I'm pleased to discover that you've found my footnote to be so unusually compelling.
[1]: https://en.wikipedia.org/wiki/Mimeograph