It's a pet peeve but:

Nothing online pisses me off quite as much as when someone pulls a Schroedinger's Douchebag. Saying something shitty in a place where tone is inherently stripped, and then backtracking with "it was just a joke ooOoObViOuSlY" is just shitty teenage edgelord bullshit.

Aside from it's inherent shittiness, when that behavior is normalized, it gives cover to white supremacists and transphobes to test the waters in every place they enter, to see if this place will tolerate and support their bigotry.

I just fucking hate it. Makes the internet worse for everyone.