> it's come up that in some parts of europe the natural decimal separator is the comma, but in combination with () parentheses these can look a lot like tuples
It's not so much a regional issue as a language issue. Traditionally in various European languages (for instance, Spanish), the comma is used.
In technical discussions it does not really matter, as people can interpret it from context. I would also guess that due to computer language conventions being consistent with English usage, and the use of pocket calculators, one can safely use the decimal point throughout, and this is ever more common regardless of what the vernacular language conventions say.
Just my €0.02, of course.