It's HTML. You can probably just open the file in a plain text editor and do a global search and replace of DEFAULTNAME with Bob Bobbington the Third, or whatever.
Not coping harder, I just misremembered. Default name is Orion though which is what I played as.
I do agree having a generic name like Mark and not giving an option to modify is iffy, specially considering it's pretty easy to write around it in SugarCube.