Hebrew doesn't have upper and lower case, so the question "is this hebrew character capital" is meaningless. So, the function in question should not return just a boolean value; it should have a way to return a third option. (Whether it's nil, a C-style return code, an exception, an enum or something else is irrelevant here.)

Actually, it just means that if you're wondering "if this word starts with a capital", you're asking a wrong question. Instead, you should be asking "if this word is a valid generic name", or "is this word a start of a new sentence", and implement these semantic queries in a language-specific way.

You have final-forms in Hebrew, although probably not at the same level of support for checking as you'd get with a script like Arabic.

That's true, but I don't think that sofits should be viewed as capital/not-capital letters: they're not semantically altering the meaning of the word in wider context, like capital letters do.