batgirl, I like how you argue your points, by showing games like yours, the Karpov and Anand gamed and others. You're teaching me how chess moves are discussed.
I just played a game as black with this opening and my opponent played 5. Nxf7. I didn't make the Traxler move, but I did win the game down a rook but ultimately up a queen with opponent resigning. I remembered this article and came back to look at it right after the game. Thanks. I'm going to remember that Traxler bishop next time I find myself in this situation. "...players...sometimes go brain-dead...", hehe, yes, esp when facing a 19th century type of swashbuckling move!
Traxler counterattack is flawed in my opinion if white defends properly.
If Black doesn't take d4 with bishop, instead he takes with pawn or knight, then the bishop will be blocked and white can take f6 freely and traxler counterattack will not happen. So arguably Black's best move after d4 is d5, and it will be rather equalized a position.
Black could (and should) meet 5.d4!? with 5...d5, as you mentioned.
Buecker's analysis of 5.d4 is freely available since a decade ago. I doubt that Black can equalize (Buecker too).
In your analysis, the move c2-c3 does not help white- he is better without it, since the knight can occupy c3:
Black has not enough for the sacrifised material.