What is an avatar ?

It's not a ghost ....

....it's just a shell....for the moment.

I think lonelygirl15 is an arty vision of this. She has a Magritte touch that made her a brilliant shell... explaining the Interest, a Hall of fame that went to shame with the hoax revelation....  Affinity with a virtual identity (0.2 of course) is high... social is mainly a mirror.
Here is a tribute.... from a white page to a full avatar.

Sources:
* Pierre Huyghe & Philippe Pareno, No Ghost Just a Shell
* M/M
* Apophenia