There's no proof. And Nexon NA Interns wouldn't blatantly show themselves because of their contract in how they interact with players. Nexon always always stresses that they won't reveal themselves in-game unless it's for an event, etc. and having the GM tag.
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First off, outside of attention, what's the incentive for someone to fake it?
Secondly, if it was that, why did he clam up as soon as I mentioned making the info public? Why also did he make such weak defenses of Nexon instead of telling us more of what we would want to hear?
Had he been a mere attention seeker, he would have kept on talking, because that contract isn't exactly common knowledge (and since he's not a GM, what's to say he's bound to the same terms? Not to mention his job description is more of a tech; he doesn't even necessarily NEED an account.)