"Ah you're American!!"

Surely a remark like that's assumes the continuing reality of the person addressed? And that cannot apply in the case of an essentially evanescent presence like that of whoever might have made a oarticular post as a nameless GUEST.

I know that sometimes it is easy to assume that the same person is making these posts, but there are no real grounds for that. That's why it's perhaps better to limit replies to posts with some kind of name attached.