He doesn't need to be sarcastic. It's just the same effect if he's sincere. Even if edw519 is sincerely complimenting Joel on 'disguising a PR piece as an objective "how to"', that's not going to be a welcome comment if Joel didn't feel he was writing a PR piece, let alone disguising it.

A sincere compliment for doing something you wouldn't do intentionally doesn't make the recipient feel good.