> Another widely-used format, LaTeX, splits the difference and actually uses somewhere between one and two spaces (by default).
Actually, it doesn't. TeX (the actual typesetter; LaTeX is a macro system on top) inserts a space that is slightly more stretchable than the space between words.
LaTeX does have the frenchspacing option, which does try to make wider spaces between sentences. What's nice about LaTeX is that you can actually tell it what you mean, like "Dr.~Strangelove" has a non-breaking space, while "add the eggs, etc.\ to the mixture" has a non-sentence-ending space, and "I went to the DMV.\@ Then I went to work." has a sentence-ending space before 'Then', since TeX takes capital+period to be an abbreviation. I suspect that Unicode has some of these things, and that no one ever bothers to use them.
Actually, it doesn't. TeX (the actual typesetter; LaTeX is a macro system on top) inserts a space that is slightly more stretchable than the space between words.