Not everyone has the same ability to infer from asituation that a sentence is sacastic (especially with written speech). Sarcasm punctuation makes the joke more accessible, which I believe is a good thing.

Poe’s law friend. Flat earther’s started sarcastic and idiots believed them.

This is not true. Sometimes sarcasm is indistinguishable from a genuinely held belief of someone you’re implying is wrong.

In spoken language we shift our tone, usually up and down randomly, while being sarcastic, which can be shown by shifting BEtweEEN CapITal anD LowErcASe. This isnt a great solution though, especially typing on mobile. Just like spoken language you can tell if someone is asking a question by the way the sentence is said, we need a marker for written language to tell the reader it’s a question, which is the question mark. If written language didn’t have this issue we wouldn’t need a question mark either. It does have that issue and we do need a question mark and a sarcasm mark.

If you repeat an absurdity in jest often enough, someone will actually believe it as truth. Marking it as sarcasm is a minor moral duty.