Anecdotally I argue a lot with people online, though I try not to be snarky or rude, but I work very hard not to argue with coworkers. So I think it's possible

Anecdotally I argue a lot with people online, though I try not to be snarky or rude, but I work very hard not to argue with coworkers. So I think it's possible you could work next to a snark merchant for years and not know it; behavior in one setting isn't necessarily related to behavior in another.