> Exactly zero of these countries are predominantly English speaking. So in other words, in English 10.000% means ten percent (with a precision of three digits after the decimal point), not ten thousand percent.

I posed a question about this a week or so ago,and got some interesting responses.[1] This one might be illuminating:

In mainland Europe we only use the metric system, even when speaking or writing English.

Also it is common to stick to the comma as decimal separator and dot as thousands separator when writing English. This convention is independent of the language used.

Same goes for date notation, dd-mm-yyyy is used (almost) always.

In Windows or Linux for example you can select the English language with Dutch localisation. It's used by almost all software developers I know.

So the answer is that countries that use a period as a thousands separator may by convention happen to continue doing so when using English. Whether you think this is appropriate is likely tied to whether you think localization applies irrespective to language or not.

1: https://news.ycombinator.com/item?id=14861871