It's not the syntax that's impressive. It's that most people who don't know C, likely wouldn't consider array access to be commutative.

It's not impressive, it's just a fun thing to show people who learned traditionally and never thought to question the commutativity of the syntax (or whether it is commutative at all)

They never said it was impressive. Just that they like to demonstrate it, presumably to people who don't know about it.