Generally, no. According to the FAQ:
How can I change the information in my profile?
It is your responsibility to keep the information in your profile up-to-date. You should especially ensure that your email address is kept current. You can alter any of the fields in your profile, except your username. Once you have registered your username, it becomes yours for life. In extreme circumstances, you may request that the administrator change your username, but he or she will require a very good reason to do so.
If you email support through your account and give your story, they might change it for you. They changed mine because I got a divorce and didn't want my old name but generally the name you sign up with sticks.
Here is where you contact them:
Forums at Splitcoaststampers
Change SCS nickname?
