Oh darn - Microsoft changed their web pages AGAIN! ugh.
Anyway, before the big latest reorg of Microsoft, they _HAD_ an
Indie developers program for XBox.... 'til September '15.
And in the documentation they had a fascinating, detailed
overview of the types of illusions you have to create in order
for your game to not be rejected by Microsoft.
One was a few paragraphs explaining in great details what is
allowed and what is not allowed in the character the player is
controlling.
I remember, for example, that you couldn't have your character
"break the fourth wall" and turn around and start talking to
you, for example.
Man, I wish I saved that page before they zapped it. It was a
deep look into the philosophy required behind FPS and XBox
gaming philosophy in general.