Louis is America still pronounces the 'S'. It's silent in Australia the way it is in France?

We say "Loo-is" compared to the "Loo-ee". So I've always done the apostrophe for words ending in S.

For instance, whenever I use the possessive form with Joss' name, I don't add an additional S. It's less to me about if the S is silent, but if there's an S at all. I remember learning that in grammar school and it always stuck.