In some parts of India (like Bengal), people usually go by a name other than their formal name. I know a person whose name is Abul K. Azad (never asked him what the K. was), but he usually signs off as Ratan except in official setting. A lady called Aparimita Lahiri introduces herself as Sona.
Is this common elsewhere: this official/personal distinction in usage of names?
In Bengal, actually, things can be more complex in a family setting: almost everyone calls everyone close by pet names or relationship terms. My father, my mother, my father's sister, my sister, my cousin, and my late grandmother all call(ed) me differently. That is a different phenomenon, though one that I haven't seen (in this magnitude) commonly outside this culture either.