I really don't like the idea of there being etiquette about how to play a game with clearly defined rules.

I would imagine that not even you agree with this statement if you take it to its logical conclusion. Say for example at in-person chess tournaments. You don't think there should be some basic etiquette about how players conduct themselves? What about a 400 pound man who comes in a speedo and covered in peanut butter and sings Sweet Caroline at the top of his lungs the entire tournament?

If that breaks the rules then whatever goes right up against the rules without breaking them, that would annoy and distract his opponent and other players in the tournament.

You don't think etiquette that puts peer pressure on some basic decorum is a good thing?