I guess now we know what Dumbledore was laughing about in chapter 17.
Oh yeah. 18 too, I guess:
“Of course you’re in here blackmailing me to save your fellow students, not to save yourself! I can’t imagine why I would have thought otherwise!” Dumbledore was now laughing even harder. He pounded his fist on the desk three times.”
Oh yeah. 18 too, I guess:
I think these are sufficient evidence that this is the real Dumbledore, not the mirror showing Quirrell what he wants.