What Latin letter(s) are you referring to?

The (classical) Latin alphabet can be fully described by the English alphabet.

What about people who do not ((speak English?) or (even use Latin letters?))

unicode names spit

if I want to name my file <turd emoji>.txt I damn well will

Any fule no that a file name is just an array of bytes (excluding the null byte and the slash). You can create a file with a name that is an invalid UTF-8 encoding. It's fun to see how much software chokes on that!