And (for names, at least) in the same language in different contexts. See https://en.wikipedia.org/wiki/Mac_and_Mc_together (poor article, but the gist is there)

I believe the same is true of de~ and van~ surnames, which are sometimes ordered by the first capital (i.e. van Houten comes before de Koninck), and sometimes not.

This means that offering a user the option of presenting a sort version of their name still leaves them in the dark as to what comes before or after it.

Which is why, I guess, going on 4 years now Mongo has has an open issue to implement unicode sorting and still has not.