As I understand it, quotation marks are used when we refer to a word instead of something external to the word. Hence
I use the word "I" to refer to me.
When we introduce somebody by nickname, we would generally use quotation marks:
Everybody calls him "Smoky Eyes".
Could or should one ever use quotation marks around an actual name? As in:
They call me "John".
And if that is not possible, why is it different from the nickname example above?