Ah I see, bringing a whole new piece of punctuation into the mix
Not wrong... just.. different. I think the way we use in North America (and others who have the same system) makes a little more sense. But, that's the way I've grown up learning math so I'm biased. Now, kids get taught the 'Engineer's' method for groupings. (Using a space between the thousands instead of a decimal or comma) which makes the most sense IMHO.
We drive on the right side of the road. Others drive on the left (read, wrong) side of the road. The name of the side we drive on implies that it is the proper way to drive. So there. :P lol