The definition of proficiency given here goes beyond that used by the CEFR, and expressly excludes most native speakers. We are told that a proficient reader "has all the literacy of an educated native speaker" and "can communicate with an elegance and style typically reserved for well-educated native speakers." This necessarily excludes most natives from consideration for proficiency in their own language, and, frankly, strikes me as elitist. As I understand the CEFR, proficiency is situational. A scientist, for example, may be proficient in, say, the English jargon used in his field, comprehending a high register of English with ease, while at the same time struggling to understand the lower registers of English he might encounter at the neighborhood bar. Proficiency should depend on one's goals.  If my goal is to speak with ordinary people, and I can achieve the necessary vocabulary and ease of communication to listen, speak, read, and write in a register intended for that audience--say, for example, at the tabloid newspaper level--then I think I have achieved proficiency in that register for that language.  I can, and should, seek proficiency at every register of a language that is important to me, including in technical fields (for example, legal jargon) to the extent this matters to me.  But why would I want to consider myself proficient only if I have achieved a level of knowledge of the language that is beyond most native speakers? We don't need to be elitist to seek or achieve proficiency.