This is a game where "detect evil" exists, but it's not like evil characters have it tattooed on their foreheads. It's a challenge to play well, and a lot of people treat "evil" (and CN, for that matter) as "I'm going to act crazy because I'm a PC and can get away with it." If your players are up to the challenge, and there aren't any codes to get in the way, there's no reason good and evil characters can't hang out.
Evil doesn't have to mean cartoonish villainy. It comes down to whether or not your players can see that.