I'm preparing my user page and having difficulties with my language levels. My English level is C2 according to the CEFR (Cambridge Proficiency), and that is considered near-native, which obviously means that I can work with it professionally. And yet, here near-native is 4, below professional performance (5)! I think it would be better to use a well-established scale like the CEFR, from A1 basic to C2 near native.
