I don't think it was in effect at GenCon.
I never thought that attaching this would remove any existing Conditions from a dude before the Fancy New Hat ruling was made, and I still thought that Knight's Chasuble was a decent card (hey, any 1 GR for 1 Inflence card can't be bad). You can still use it to protect a dude from Conditions, meaning they can safely move to locations with Tummy Twisters, avoid being Lost to the Plague and can't be removed from play with Forced Quarantine (I think they can still be targeted by the job, and the leader would still get the CP if successful though). With horses being a strong choice at the moment, the React is a nice counter to Run 'em Down and Ridden Down, and means that a Pistol Whipped dude may be out of the fight but isn't stuck at home booted. Plenty of other effects it helps against too.