Autistic Hedgehog

My best guess on the matter is this: Rather than being emotionless, autistic people have a tendency to feel emotions very deeply and strongly, and we can’t always hide that. Sometimes the reason we can’t hide it is because we don’t even realize that our feelings are showing in the first place. (There’s nothing wrong with this, even if society likes to act like there is. Don’t let other people squash your emotions.)

So what happens is, when we’re around someone we like—not necessarily, and in fact often not at all, in a romantic way—we’re happy and comfortable. We relax. Our happiness and comfort comes out, and for many of us it’s just easier to act like ourselves, and we’re often fun and funny people. Society has some pretty messed up ideas about socialization and the meaning of social cues (aspects of rape culture reflect this pretty well) and thus it gets read as flirting when it’s merely happiness and comfort expressing itself unrestrained.

Conversely, this would also explain why a lot of us have trouble flirting on purpose. If we’re romantically or sexually interested, we’re invested in a different way, one that makes it damn near impossible to be completely at ease. Instant recipe for awkwardness. 

A caveat: Those are simply my thoughts on the matter, and are based on observation, of myself and of other autistics. I can’t really back it up with science.