Johnchick in Russian is like saying Johnny in English. It is just a cute way to pronounce your name.
I do not like names with more than two syllables. It leaves more room for me to mess up pronouncing the name. Double names like Mary Kate are the worst. I worked with a girl named Anastasia once and could not bring myself to talk to her because I would have to pronounce the long name. Nicknames help me make friends.