In general, No...and definitely not by the player. There is no way for a player to change their username. Why? Because poker is played between people and your style and history is associated with your username. Changing that gives you an unfair advantage against others.
But there are some extremely rare exceptions, for instance where a player can prove they are being harrassed or persecuted in some way. In that case you can contact support at NoPayPOKER who will make a judgement call and possibly change your username if suitable.