Comma for decimal separator, and point (or sometimes 'postraphy) for thousands separator if there is one, is very common. IIRC more European countries use that than don't, officially, and a bunch of countries outside Europe do too.

It wouldn't normally necessitate not using comma as the field separator in CSV files though, wrapping those values is quotes is how that would usually be handled in my experience.

Though many people end up switching to “our way”, despite their normal locale preferences, because of compatibility issues they encounter otherwise with US/UK software written naively.