I think as long as you keep in mind that it's the player using the Moon Sentences, not the character, you can make them as difficult to use as you want and it'll be fine. I'm thinking of the part where Jack uses a sentence that's something like "The casino always catches cheaters" (been a few weeks so I can't recall the exact wording) to have the bouncer catch an unrelated cheater, which lets them sneak in while the bouncer is occupied. So, "Secret Police on moon always arrest their target" or something like that could still be used by the player in some creative way. Maybe having the secret police arrest someone else, or maybe the PC wants to be arrested to further some other goal. A better sentence would probably have a more open-ended verb than "arrest" so the player can find a loophole.
Ideally I think the Moon Sentences should encourage the players to use them in clever ways, and one approach to that is writing the sentence so that it isn't obvious how the player should use it, which forces them to find a clever way if they want to use it at all. But I think "Arguments on Areteas are always won by whoever speaks most" is really good even though it's very clear how the player might use it, because it's also very open to being used in unexpected ways and it demands the player use it creatively even when it is used in the expected way.