It has been said by others here that "escaping a reputation" would be their main concern. As others have also said, if this is done correctly and like other games have done, it wouldn't matter because their name would be changed across the board. Even if you went into your blacklist and saw a name you didn't recognize, it would be safe to assume you put them there for a reason. If a friend changed their name, chances are they would have told you. As Mahri said as well, if they are an ass then their new name will get blacklisted or reported just as often. If they are using it to actually make a new start, great! It has been suggested that this should only be able to happen once in a certain time frame, making it rather expensive in game, making it a RL pay service. There have been many ideas for solutions to this problem that's not really a problem.

Other games have this feature. They have not exploded from all the people with bad reputations running around changing their name.