3.141,592 - Germany formats numbers that way.

Here in Switzerland it's even worse because it depends on where in Switzerland you're formatting the number (French parts have different rules from German parts) and whether you're formatting a number as a plain number or a monetary value.

if it's money, you use the . as the decimal separator everywhere. if it's just a number, in the French parts, it's , in the German parts the .

The thousands separator is ' everywhere

surely this must routinely cause horrific mistakes in things like bank transactions?

Norway as well

In my country most people do not really use thousands separator, so here it would be either 3141,592 or 3 141,592.

At least in currencies it is very common to use space as a thousands separator.

Note that some languages don't follow the "break at thousand, million.." pattern, most notably south asian languages that break at the lakh and crore boundaries.

3141592 thousandths. Integer is beautiful.

3'141,592