Uranium235
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"Shall we agree to play Heroes 3 online?"
Added 11 minutes later
Actually, it's easier to guess the author than the characters. Not from the chat, not an active poster, hasn't submitted another story (most likely), participated in the contest (most likely). Dag is out because he's trying to guess the characters. That leaves Vishmaster and Majerson, one of them is the author.
Added 13 minutes later
Let's vote to eliminate Vish. He's the author of the fake note.