So we just learned that conditions are considered mission rules for the purpose of conflicts. Assuming that you can't have negative surges or evades this means that any effect that adds a surge or evade will get around it. Am I right in thinking this, is my assumption wrong or am I missing something else?

Where does it say that Weaken is considered a mission rule?

I'm pretty sure it's not intended to work that way, but who knows it seems to be worth a rules e-mail to FFG if there isn't a ruling somewhere already.

EDIT: I just saw the e-mail ruling on conditions being mission rules. It does seem then that surge adding affects will work around Weaken.

Where does it say you can't have a negative surges or evades?

The entire point of "Weakened" is applying a negative evade while defending and a negative surge while attacking.

Where does it say you can't have a negative surges or evades?

I never even noticed that. That's a good point and maintains the strength of Weakened as an awesome condition to inflict on the right figures.

So you can exhaust a card (in Campaign) to add a surge but Weakened will still subtract from the final result.