A Masterpost of L’s Autistic Traits and Examples of Him Doing Autistic Things In-Canon
bad/improper posture while sitting and standing
speaks in a monotone voice
needs help bathing and getting dressed
sits with his knees pressed against his chest (common in Autistic people, possibly a pressure-related stim)
only eats sweets (“samefooding”)
always wears the same clothes
avoids wearing socks (possibly because of sensory overstimulation, and possibly because socks limit mobility of his toes and prevent him from stimming by wiggling and tapping them like he normally does)
holds most objects using minimal touch/contact
does/says inappropriate things without thinking about social consequences
considers Light his only friend (I would argue that Watari is his friend, but maybe the reason he doesn’t count him is because he sees Watari as more of a father figure than just a friend.)
presses and tugs on his lips a lot
his meltdown upon hearing about Shinigami for the second time
“I’ll give you this strawberry if you keep it a secret.”
self-described as “childish” (Autistic people are often seen as childish, and many embrace this as a part of their personality.)