Well, keep in mind that Harry did just see Voldemort’s reflection with Dumbledore’s family before the Confoundment wore off. I don’t recall the mirror doing that in the original canon, but it might just have been changed to make the scenes flow better rather than due to a specific mechanical change in how the mirror is supposed to work.
What the man might be seeing there, Harry could not tell; to Harry it seemed that the flat, perfect surface still reflected the room behind it, like a portal to another place.
Well, keep in mind that Harry did just see Voldemort’s reflection with Dumbledore’s family before the Confoundment wore off. I don’t recall the mirror doing that in the original canon, but it might just have been changed to make the scenes flow better rather than due to a specific mechanical change in how the mirror is supposed to work.
I thought Harry couldn’t see that.