There's the common adage that sarcasm needs a "tell", otherwise people might take you seriously. A group of previous colleagues taught me you actually have to go one level deeper:
Not only does your sarcasm need a tell, you need to have previously provided enough evidence that you're not actually an asshole. Otherwise, someone can be sarcastic all day, but no-one's really sure whether they're trying to be funny, or actually offering genuine asshole views coated in the plausible deniability of "sarcasm" for those who don't agree.
"I really can't tell if you're joking" is the first warning flag.
Not only does your sarcasm need a tell, you need to have previously provided enough evidence that you're not actually an asshole. Otherwise, someone can be sarcastic all day, but no-one's really sure whether they're trying to be funny, or actually offering genuine asshole views coated in the plausible deniability of "sarcasm" for those who don't agree.
"I really can't tell if you're joking" is the first warning flag.