Why do you say fanon! Light is Mikami? Just curious,as I like both guys in the manga.
... the ask I just answered about Light 'splitting obsessively into good and evil' and 'seeing himself as a chosen one' is a pretty good example, actually. Mikami does these things, Light does not.
But when I made the post, I was actually thinking of smaller things.
People like to make Light out to be some extreme stickler for the rules, a super-nerd who would never do something improper. This is not true - the kid trespasses at abandoned buildings for a hobby. He knows how to keep up appearances, but he has no intrinsic need to be Right and Proper at all times.
(And then you get things like the TV Drama literally giving Light a chunk of Mikami's backstory.............)