How violent do you think this reaction would be? Two characters are time-traveling in sync, but they get physically separated. The language gets too complicated, so treat their current frame of reference as the present. One character gets into trouble, his counterpart saves him, but admits that he's from the future, not the true counterpart. With an established rule about how dangerous it is to go mucking about in time, how would you react to the older counterpart not saying anything useful?
It might be best to keep it simple. Have Traveler B say nothing of being from teh future after saving Traveler A. Later, in the future, you write the scene from Traveler B's POV where he goes back in time to save Traveler A. Or: After Traveler A is saved, he notices something is different about Traveler B (different clothes, or haircut, or etc.) but before he can ask, Traveler B disappears. When he reunites with Traveler B from his timeline he notices his clothes are as he remembers. He asks about being saved, but Traveler B knows nothing of it since it hasn't happened yet.
Actually, his appearance will never change. Having traveler B mention that he's a future incarnation is the simplest option, and replaces a huge but boring conflict with some interesting awkwardness. I later have a minor character being instructed to follow a script because he talks to the earliest time-traveling incarnation of Traveler B. The Sue by then has the ability to watch without being observed, and laughs hysterically because the minor did not follow the script. (He treated Traveler B as familiar, remembers the script too late and refuses to follow it, time isn't damaged that much.)
