One thing I find interesting about discussions of typography in Cyrillic is how poor the overall readability of text is in most fonts compared to Latin because of the relative scarcity of risers and descenders (e.g. pqlt etc)
One of my tutors at university claimed that she was able to read 9th century manuscript Cyrillic faster than modern printed books because the orthography was more varied and easier to scan/speed-read.
(That wasn't something I found to be true)
> Standard space, word space, space per se, is the symbol typed using the widest key on the keyboard.
What a strange non-fact to include.
This also makes me think of drumming. There are the sticks that hit the surface and form a pattern of sounds. Lots of different kinds of spaces embedded there!
There is something oddly beautiful in invisible complexity. These little tweaks and minuscule details without which the whole would suffer in quality.
I learned to type in Junior High School in the nineties, and it is extremely difficult to leave a single space after a period. Like that, it took a huge effort for me to break conditioning.
Of all spaces, the space between sentences is discarded because a period is whitespace. However, kerning partly removes this.
Perhaps this is why monospaced fonts are so readable? I like having double-space between sentences.
On the layout side rather than the "what spaces are available" side, I really recommend https://gwern.net/doc/design/typography/tex/1981-knuth.pdf , the paper in which the Knuth-Plass algorithm for paragraph layout is defined. (The Knuth-Plass algorithm decides how wide spaces should be on each line and which choices of hyphenation out of some predefined set should be used to lay out a paragraph.) It's super readable and generally quite joyful. Knuth describes TeX as a "labor of love", and it shines through that paper.