On the
Art of Battle page, it says, specifically---"If you react at exactly the right moment, you can parry the hit and throw a powerful counterattack to your enemy." (under 'signs and feedback')---which I'm guessing means moving the stick the direction you intend to block at the same moment an attack would hit, or at least in the midst of the attack animation, rather than holding the stick in the direction prior to the attack being executed---in a similar way to Assassin's Creed counter system (or any other melee-focused game with a parry/counter system), but a stick motion (given For Honor's blocking system) instead of a simple button press.
Maybe ask about it specifically, if you do get another chance to play.
And all the gifs in my last post were taken from Gamescom playthroughs, so unless they brought a less complete build to PAX, it should be the same thing.
Thanks regardless, and my envy cannot be contained. Hopefully, they'll give some indications or details for the beta soon, so those of us that can't make it to events will be able to test these things out for ourselves. This suspense is deadly.