It's even worse than that. Office on my work computer is set to the English language, but my locale is French and so is my Windows language. It's saving semicolon-separated CSV files with the comma as a decimal point.

I need to uncheck File > Option Advanced > Use system separators and set the decimal separator to a dot to get Excel to generate English-style CSV files with semicolon-separated values. I can't be bothered to find out where Microsoft moved the CSV export dialog again in the latest version of Office to get it to spit out comma-separated fields.

Point is, CSV is a term for a bunch of loosely-related formats that depends among other things on the locale. In other words, it's a mess. Any sane file format either mandates a canonical textual representation for numbers independent of locale (like JSON) or uses binary (like BSON).

That, bad specs, weird management/ timezone/ governance/ communications and random \n\r issues transformed a 2 day fun little project into a 4 week hell. I will never work with CSV in France ever again. Mostly because of Excel, normal CSV nice.

If it only was that easy. Experience has shown that the only reliable way is to run heuristics against the first few lines of the file.

There are office programs that save CSV with the proper comma delimiter regardless of the locale.

There are people who run non-local locales for various good reasons.

There are technically savvy people who have to deal with CSV shenanigans and can and will send it with the proper comma delimiter.