I am from Europe and always use a comma as a decimal separator. Thus, in all previous publications I have used a comma as a separator, noone ever objected. We recently submitted a new manuscript and one reviewer comment we got was that we should use points instead of commas as separators. The article was written in English; the journal has a style guide but the separator issue is not covered.
Personally, I think this request is weird, as both versions are widely used and not, like non-SI units limited to very few countries. Also, I don't think that anyone will mistake 2,34 mm as anything other than what it is supposed to mean, even if they would rather write 2.34 mm instead.
So my question is: is there an (unwritten) rule about that point instead of commas should be used as separators in academia that I don't know about or is the reviewer simply trying to change the data formatting to their own preference?