Yeah, Jack hasn't quite worked out that the rules are different here. He may well be in for a bit of a shock.
His eyebrows go up as his sword slashes down Spike's face in the exact place where he bears a scar across his eyebrow. "Huh, did she do that?"
He's caught up enough in wondering about it that he doesn't realise Spike's moving in again until he feels pain hit him in his knee. The knee gives on him and he staggers again, more this time, grunting with the pain, instinctively flailing with the sword to try and keep Spike at bay.