User blog comment:Señor action/editing you shepard in mass effect 3/@comment-4491632-20120226013846

Assuming the latter. There would be no reason in the story for the change of appearance and powers, but they had it in ME2 and everyone seemed to know it was Shepard pretty well. It's just there for gameplay purposes. If you liked the decisions your character made in the game but had a problem with his/her class or appearance, for example.