As is suggested in http://php.net/manual/en/function.number-format.php
a "French notation" is number_format($number, 2, ',', ' ');
where thousand separator is a space.
So is acceptable to set space as delimiter.
But this generate problems for example in Payments where in input field we get "1& nbsp;225.50"
And problems are when we use comma as decimal separator too ......
I suggest to rewrite the number_helper and check and fix usage of this functions.