this is why I usually use spaces to separate thousands, so that I don't confuse people expecting either notation.

The standard where I'm from is also a period for thousands, and a comma for the decimal fraction, but reading as much English scientific and computing literature, I am well aware that the period for decimal fraction is almost a de facto standard. So I tend to use spaces for the thousands and a period for the decimal fraction, so that anyone who sees the spaces can infer what the other symbol means.

Fortunately I am not aware of any notation system that uses a space to separate the decimal fraction :)