I’ve found many parallels between cinematic street fights (not like people getting robbed, more like mobsters with complex relationships ducking out to the alley) and engaging in sensitive and/or extended arguments with people. Following the etiquette prevents things from going sideways!

No good street fight starts with a surprise attack. Express your intent to fight, circle each other a bit to give the other person a chance to walk away. Are their fists up or are their hands up? This is your first demonstration of respect for the other! It sets the tone and prepares for escalation.

Communicate the purpose of the fight

People often start a street fight with phrases like “let’s settle this once and for all”, and if it’s responded to with “that’s what I want too”, it’s relevant for understanding the dynamics! Sometimes it doesn’t have to be explicit, like if an instigator is obviously angry their goal is probably some kind of catharsis.

No kicking when they’re down

Bullying people after defeat is apparent is often counterproductive, and may cause them to feel resentment and ruin the goal of the street fight. Obviously bad etiquette.

Don't bring a gun to a knife fight

In social situations, it can be bad mannered to end a conversation early by squashing the premise or some core idea. Fight with your left hand if you need to (perhaps it’s always good practice to steelmanning), it shows respect and is better for achieving cathartic street fights.

Take breaks with active communication

Perhaps the best part of a street fight is when you’re both a little tired and need a second to catch your breath. It’s ok to take these! It’s also a great chance to do some meta communication, like “you put up a better fight than I expected”, “I can’t believe you’d stoop to biting” or “ready to go again?”.

Escalate at a reasonable pace

Don’t suddenly launch an entire different style of attack or start going harder. Escalate at a reasonable pace that can be silently agreed upon. Post-breaks are a good time to escalate.

It’s honourable to help the other person up

This is not really etiquette, but it's nice! It’s important to know that accepting a hand does not necessarily mean that the fight is over, and that offering a hand should not be out of condescendance.

Express your updated sentiment upon completion

Whatever the purpose of the fight was, it’s good to communicate before leaving. Like, “we’re not done here”, “I hope you’ve learned your lesson”, “ok fine [you win]”, or even a simple “I’m glad we did that”. It’s a good time to appreciate that maybe some catharsis was achieved even if your specific goal was not met. Leaving a fight with more respect for your opponent is always a win!

Avoid rehashing

Street fights in spirit are ephemeral and spontaneous. Unless something was communicated to imply otherwise, it’s also bad etiquette to try to rematch or air out the problem again. It’s certainly ok to ask though!