At the bare minimum, if someone asks for clarification it should be given How far are you supposed to take the clarification?

Enough that the other party can understand.

Does this apply to authors and artists too? Should all metaphors have an explanation?

There’s a pretty big difference between literature and art, and online comments.

Do neurodivergent people not get to enjoy literature and art?

They do, sure. They also are able to know that what they are consuming is literature and art, and not a random user being deliberately obtuse.

I disagree. I feel like if you’re able to enjoy literature and art you’re able to read internet comments too.

Have you spoken to neurodivergent people about this? I won’t pretend to speak for them, but the idea that tone should be clarified upon request is something I’ve seen in neurodivergent communities. It harms nobody, if clarifying ruins the joke then the joke wasn’t actually funny to begin with.