I also think the romantic reputation system is kind of annoying. I believe it should also be based on traits. I think that flirty, inappropriate, and hopeless romantic Sims should be the only ones automatically accused of cheating, and have worse reps, and that the insane, mean spirited, hot headed, over emotional, and neurotic Sims should be the only Sims to automatically accuse.
But, in my opinion, the whole romantic/attraction system has been flawed, even in Sims 2!