Once the determine_number_style stuff is in place this will work better.  At the moment it's still looking at the numbers in isolation.

Regardless, what you see here is actually the intended behavior.  As I understand, you would like it to check that if I am calling something a thousands separator it's got 3 digits after it?

I can do this. I even considered it, except that it broke a test I added for the example (with a broken number) from issue #207.