I've gotten considerably more replies here than on Reddit from people who don't understand sarcasm.

Pretty sure it's the tism.

Neurodivergents being overrepresented likely accounts for some of the tendency of people mistakenly taking things literally on Lemmy. But I think a bigger issue is just a lack of media literacy. People tend to close themselves off from opposing viewpoints, and what does filter through is often exaggerated or otherwise misrepresented to make it easier to ridicule. This pattern leads people into thinking something intentionally absurd is in fact serious. Poe's law is something easy to observe on other platforms too, but it's worse on a platform with an especially political and nondiverse userbase.