Another lovely thing was "Time travel is impossible." Dude, the core audience of your show knows that it's not.
Though it would have been interesting to make it somewhat a mystery if Archer was just crazy, was being tricked, or if he really was in contact with a time traveler.
T'Pol had an almost religious devotion to the Vulcan Science Institute's declaration that time travel was impossible, even with tons of evidence to the contrary.
Hey I think time travel is impossible too. But if I start seeing evidence of it thrown in my face, I'm sure I would start to reevaluate that belief.