It does sometimes make sense to have identifiers in non-English languages. If could be for a DSL, or it could be because the business logic concerns concepts which is not trivially translatable to english.
And this works right until a developer who doesn't speak the language will have to deal with that code, which will happen much sooner than you'd expect. Half of the fun is figuring out the meaning of variable names, the other half is figuring out how to type ß on a non-German keyboard.
Minor side note: I cannot for the life of me figure out why other operating systems won't borrow Apple's fantastic input scheme, in which this something as simple as a ß isn't a big deal. Need an emdash? Easy, option-shift-minus. Need an ñ? Easy, option-n-n. ß, ≠, ¡, ÷ or any number of other relatively common symbols? Easy. Most of them are even fairly mnemonic (e.g. ß is option-S, ¡ is option-1, ≠ is option-= and ÷ is option-/).
Lion made this even easier by stealing iOS's input scheme: Hold down a keyboard key for long enough and you can pick a special character out of a context pop out. îïíīįì šéē
I wish JS was better-suited to embedded DSLs. But without operator overloading, with required parens on function arguments, no (standard) method_missing, no atoms, and a limited set of characters for identifiers, it's pretty limited.
