‘Autistic-coded’ is a fandom term to refer to a character that hasn’t been canonically confirmed as actually being autistic, but exhibits some of the qualities that one might find within someone who is autistic. Think Spock or Data from Star Trek, if you’re looking for an example.
Autistic-coding is, ultimately, a headcanon for a character, as the moment their potential autistic-ness becomes confirmed, then the character would just be autistic. Connor’s disregard/misunderstanding of social cues and hyperfixation on his mission often lead people toward thinking that Bryan’s portrayal might be inspired by autistic people, or that he might qualify for a diagnosis in a Human!AU. Neither of those things have been confirmed (at least to my knowledge) so right now, he’s just ‘coded’ as autistic within the narrative.
However, just as in life, fandoms overwhelmingly tend toward ‘diagnosing’ white male characters as autistic-coded over female characters or characters of colour, despite those same characters exhibiting the same ‘symptoms.’ My friend @anonymousmythicalcreature wrote a wonderful essay on why Markus is autistic-coded, and I think there’s enough room to argue that Kara is too. But those headcanons aren’t as widely accepted as pseudo-canon amongst the fandom as the juggernaught that is the Autistic!Connor headcanon, with their ‘symptoms’ often dismissed as a fault of Jesse or Valorie’s portrayal or an aspect of Markus or Kara’s personality that makes them boring or unrelatable.
Which, ultimately, is the point of this post.