We're currently developing a multi-country / multi-language application and face the issue of not being able to adjust the decimal notation. I'm not the first that is annoyed by this but I hope I'll be the last.
Previous questions/ideas on this topic:
A default datetime format is already configurable, so why not the same for the thousands separator and the decimal point? Maybe this should be limited to a '.’ and a ',’ and there could be validation on that they are not the same, but I could also imagine that it is possible to disable the thousands separator.