I'm currently playing CoH, and I have seen quite a few copy cat characters in game, but for the most part everyone comes up with something original. The character creation can take a very long time, for me I probably spent at least 45 minutes creating my character.

If NCSoft has to prevent character copies, I am not sure how they could do it on the technical side. All it takes is someone to produce a look alike with just one element off color from what they define as off limits. It would then become necessary for the support staff to examine every new character with some sort of Marvel cheet sheet in hand, raising their support costs, and likely the cost to play the game.

As PvP hinted at, it's like sueing pencil makers for people drawing Marvel characters.