To the best of my knowledge, no one has treated “rhythm” in any way rigorously, and it’s mostly just a crock, something that sounds good on paper
Ironically it does sometimes look better on paper - specifically on cheap, thin paper with double-sided printing where ink showing through from the reverse side in the inter-line gaps can be distracting and unattractive.
So perhaps you're wrong about it being utterly without reason? It makes sense to maintain an exact vertical rhythm in digital typography any time you're displaying your content on a thin, double-sided monitor where the image from the reverse side bleeds through. Not sure how much use it is apart from that though.
Amusing indeed; I was actually thinking about my primary Bible at the time, which certainly benefits from rhythm, including having things like book titles and page headers fit the rhythm. Paginated media can certainly benefit from rhythm, most obviously when double-sided with bleed but even when not, as you flip through.
I meant “no value in scrolled media”, I just didn’t express it so because I hadn’t thought it through carefully enough. Note that digital media can also be paginated; a PDF where you switch pages rather than scrolling, for example, or content that might even normally be scrolled but viewed on an e-book reader, due to the physical properties of e-ink panels; and these things can definitely also benefit from matching alignments and dimensions across pages even without the bleed issue.
Still, even though I was expressly thinking about it, I somehow didn’t connect the dots that maybe this idea of rhythm is a carry-over from the print era. Thanks for pointing out that link!
(My primary Bible is a second edition RSV, where the layout of the first edition was reused and only tweaked where necessary. This leads to minor ink weight differences within some pages, and a very few instances of visibly wonky layout, with elements a fraction of a millimetre from where they should be, or slightly crooked. The most significant weirdness for rhythm purposes is how John 7:53–8:12 was restored from a footnote to the main text, and the column it’s in has one fewer line than normal, with a half-line break between two paragraphs, and the rest of the line’s height distributed through the column’s leading. I’ve been paying a lot of attention to its typography recently, as I start making my own software designed for Bible reading, which is basically a space where there has never been a single option that I would consider good.)
Ironically it does sometimes look better on paper - specifically on cheap, thin paper with double-sided printing where ink showing through from the reverse side in the inter-line gaps can be distracting and unattractive.
So perhaps you're wrong about it being utterly without reason? It makes sense to maintain an exact vertical rhythm in digital typography any time you're displaying your content on a thin, double-sided monitor where the image from the reverse side bleeds through. Not sure how much use it is apart from that though.