Playing the Tantive campaign tonight, we had a situation where two identical face up damage cards were dealt to the aft section, and both were Reactor Leak. (The card's effect is to reduce the energy gained by 1.)

Should both of these cards have had a cumulative effect of reducing my Tantive's energy generation by 2?

I'm trying to think of any similar situation in regular damage decks, or a general principle that identical effects should stack.

Yep. No reason they shouldn't.

An equivalent in standard play would be the crits that reduce agility or primary weapon values.

There is also something in the FAQ about how, when you have 2 identical crits that you can perform an action to turn face down, you have to do so for each separately.

There is also something in the FAQ about how, when you have 2 identical crits that you can perform an action to turn face down, you have to do so for each separately.

There are also times a card is turned face down when something else occurs. In those cases seeing that trigger can cause multiple cards to flip at the same time. An example of this would be Blinded Pilot.