> I'm curious if anyone can think of any other non-alphabetic characters used in legal names around the world, in other scripts?

The Catalan name Gal·la is growing in popularity, with currently 1515 women in the census having it as a first name in Spain with an average age of 10.4 years old: https://ine.es/widgets/nombApell/nombApell.shtml

beautiful map of the Catalan Countries when you search for that name here