My close friend Joe plays an attack card. Joe is a cool guy and doesn't afraid of anything, so I choose not to reveal my harmful reaction card, Super Spiky Shield. Schmoe goes next. He is not a cool guy. He plays an attack card so I spite him by revealing the reaction. Tough luck, Schmoe!
Yep. The ninja-comment said something about not saving the reactor, though. If the reaction also protected the reactor, would that be enough to solve the problem? I guess it depends on how powerful the counter-attack is. Would I let Joe make me discard down to 3 (one of which is my reaction that I'll have to discard if I use it) so that I can put a Curse in Schmoe's deck? Several Curses (or to take an example from something that actually already exists, a Curse and a Copper)? And then, I don't know if Schmoe is going to attack this time around...
What if the reaction were compulsory? But then I guess there is no way to keep people honest except "in games using this, all players reveal their hands in response to any Attack", which in turn makes every other reaction compulsory and also strengthens(?) the attack by having everyone give information to everyone else.
Moreover, given the reaction, you can't allow it to be revealed more than once. You have to put in a mechanic such that the reaction gets discarded or set aside.
Depending on the counterattack. If it's "the attacker discards down to 3 cards", then it doesn't matter if that's revealed multiple times. If it's "the attacker gains a Curse", it definitely does.
If that isn't worded with extreme care, you get into situations where you think, "I could use my reaction now, but Schmoe is winning so I should save it, just in case."
I'm thinking my concept of "politics" doesn't include situations where the second-place player is incentivized to play differently against the leader than against the loser, simply by virtue of the current standings. It's not like we're actively co-operating with Joe here.
But maybe we need a separate thread to discuss just what "politics" means to people