What's the word that can be used to describe someone who has mastery over English?
They have command over the way that they use English, and they are perceptive in how they read English.
Doesn't have to be English in particular.
Such a person would be a good debater, good orator, capable of making astute critical analyses of works of literature, reading dense texts, etc.
I don't mind whether answers are nouns or adjectives.
You are a ______ (noun like "virtuoso")
You have a ______ (noun like "mastery")
You are _____ (adjective like "erudite")
Not the same question as What do we call a person who is really smooth at talking? because I am interested in what to call someone who is good at comprehending English and its nuances, is effective at using and interpreting the language. Not just someone who is a smooth-talker. The other question doesn't sound profound enough, especially not the answers. My guy's got gravitas about him, an academic kind of elevated status.