I don't want to write this at the end of Seb writing analysis, I want my readers to understand, what follows is a THEORY.
A theory based on what I see on his signature and on 15 years of graphology hobby, but still, just a theory.
So, graphological facts are : a signature is a self-projection. You usually choose it when you're a teen. You write who you are, in your mind. It will evolves (bigger, smaller, simplier...) but it almost never completly change. If you choosed to write your name at 17 years old, you won't suddenly choose to stop at 50 (or you're about to commit suicide, euhm euhm)
When he was a teen, Sebastian choosed to write his first name ABOVE his familly name (interesting and relevant). He did not choose a vaporous/impersonal signature, he identified himself clearly : I am Sebastian, from the Stan familly.
The way you write things is always important. If you're in love, you write the word "love" bigger, you draw little hearts all around...when you write your first name in your signature, you say a lot too.
Sebastian writes his first name, and then, he...hum...he kinda slays it :D
Sometimes, he draws train tracks around "Sebastian", that's what you draw when you need stability, something to cling on to.
Sometimes, he's surround "Sebastian", he's drawing a circle all around him, something soft and sweet, a place to rest.
Most of the times, he draws both.
When he writes "Stan", he does not delete it or surround it or draw anything around. Stan is almost peacefull, when he thinks "Stan" there's nothing violent in is mind, things are Ok, so he writes it peacefully. See the a of "stan", it's big and it's a love circle : tenderness.
So Sebastian's got issues with Sebastian, but not with Stan.
The theory is : Sebastian's been bullied at school. reason why, as a teen, he started to draw circles around "Sebastian", to protect him. He does not protect him from his familly, so he probably protects Sebastian from the other human beings around. And when you're a teen, other people around are teens too. So I think Seb's been bullied at school. It's a possibiility. He was romanian, he was 12...well, you know kids...He probably had very very bad days. He probably had to protect himself from mokery and to fight against low self elsteem for few years. Most important years of a lifetime.