A lot of folks think that Knuth-Plass is the optimal solution for good looking text, for all text. It really only considers Latin, and even then has restrictions.

Some fonts have the space character in the kerning table, and possibly (although super rare) in the "ligature" table (gsub). (https://www.sansbullshitsans.com/ is an example of a font with a space in gsub, "paradigm shift" maps to a single glyph).

If you want to go really deep on how complex some scripts are take a look at: https://r12a.github.io/scripts/arabic/arb.html#shaping