Chess Etiquette

Not really, no. Online there are no rules.

Although if you stop trying to play well, that's generally rude, and people generally won't accept or offer a rematch.

For example shuffling your king back and forth because it's the only piece you have left (the exception being when clocks are low).

Or something like you have an obvious mate, and you don't play it.

Oh, by the way, people make up all sorts of rules that don't exist like saying "gg" after a game.

The reason they don't exist is because there's always a second set of people who insist that e.g. saying "gg" is gloating and rude and you shouldn't say it.

Similarly for rematches (offering or accepting), same for chatting or disabling chat, and same for resigning. Some people go nuts if you violate the obscure little rules they make up in their little heads.

But the thing I said about not taking the game seriously anymore, I'm not aware of that being controversial. I think everyone agrees on that one.