[OJFord]

I'm not sure what you mean by working both ways, I'm saying as the speaker one respects the subject's title, even if not 'recognised' natively.

For example, I'm not Catholic, but I would of course refer to Pope Francis; not 'Mr Francis', or anything involving his birth (as opposed to regnal) name.

[pseudalopex]

I think the norm is the current surroundings, not wherever the subject is from. Dr. Smith is Smith-sensei in Japan. The New York Times is known for its use of courtesy titles, and it calls knights "Mr.".

Pope is a high office, and Francis is his chosen name. It would be rude of you to call him by his birth name; it would be rude of him to insist you call him "Your Holiness", although you probably should if you're visiting the Vatican.