It's a very simple question, and I think the answer's "no, except for countries that do, and even then it's frowned upon", but I can't find any sources. When I google this question, I get articles talking about the countries, but not the languages.
The closest I can get is this article which states that the Francophone part of Canada uses the decimal comma while the standard in the rest of Canada (i.e, the Anglophone parts) is the decimal point.
It also states that:
"Australia, New Zealand, as well as the islands and archipelagos close to them, use the same system as the rest of the Anglophone countries. Therefore, the decimal separator they use is a point." (emphasis added)
This seems to support my claim, but it confused the matter because, last I checked, "Anglophone country" means "country that speaks English", which includes South Africa, which they had just stated uses the decimal comma.
There was also this Quora post (Thanks @Hachi) that says only three Anglophone countries use the decimal comma: Canada, South Africa and Namibia. However, all three countries use both the point and the comma. It also clarifies that Canada only uses the comma when using French, and the point when using English.
Further research indicates that South Africa, like Canada, is officially multilingual, with no less than ten official languages. This implies that South Africa could be like Canada and use the comma in its other languages but not in its English.
That said, according to the Wikipedia article on the Decimal separator (Thanks @Xanne), South Africa adopted the decimal comma when it adopted the metric system, but "some English language [publications] continue to use the decimal point" (this, unfortunately, needs a citation).
Meanwhile, Namibia, although officially Anglophone, is almost entirely ESL, and was originally a German colony, which is important because Germany has always used the decimal comma. This seems the most likely source for an English dialect that prefers the decimal comma to the decimal point.
So, to reiterate, are there any (native, standardized) styles of English writing that use the decimal comma rather than the decimal point?
