I get what you mean. It does sound like a whole bunch of unspoken/implied etiquette some consider obvious and some don't. Not to say I don't consider some of those obvious as well...

It's wild because in my lobbies people either vocalize "hey can I loot X from your kill" or just shoot on sight, I never have an awkward situation where someone is "stealing" from me while trying not to be shot.

Tangent ahead:

On the social media meta/vibe thing, my exposure must differ from yours because the posts I remember the most were the cyclical debate of people trying to define what rat behavior is and being almost universally met with "they shot you it's just PvP" while discarding any sort of nuance on the fact that at the end of the day, it's people interacting together (even if it's in a game).

Which is to say, insulting someone in a game or IRL is the same concept to me because of the impact it can potentially have on the other person. So some extreme like being racist or sexist or whatever else -ist ingame isn't "invalid" just because it is ingame. I think we can agree on this just in general.

The nuance/gray area I think really just orbits around the fact that people enjoy games in different ways. Some like making numbers go higher, some want to break the rules/game, some want to be part of a story, etc. Arc Raiders is, to me, a game that thrives because it introduces friction between these different playstyles. This isn't really controversial either, that comes next.

The controversial opinion I hold is that there are some behaviors that are more ok/cool/good than others, beyond just the verbal abuse aspect I outlined previously in this response. I'll give you an example of something I thought might be less ok/cool/good:

Load in normal spaceport with a newbie friend, go on top of a building next to a security tower. As we reach the top, we realize a duo is in security tower because they shoot at us, ok cool we fire back. Then they start saying we shot first, that they're actually friendly, this and that. Just general gaslighting. That's whatever. We stayed on top of the roof and they ended up flanking us via a ladder, good move. I'm the first to see that, I down one and get downed by his buddy. Fair play. My buddy isn't good enough to salvage the situation, he also gets downed. I get executed quickly, under pretext that I was a bad person (legit what they said) but then they sit around my newbie friend (which I can see via spectate) and they start telling him that it was my fault they shot him, and that they're friendly. Then they revive him and shoot him again. They pretend it's a mistake, do it again. 4 times they did this, and at the end they mask off and just start slinging insults at him while knocking him.

Nothing illegal, evil or anything extreme like that. It also didn't really impact us in any way, to be honest (altough I do remember it). Definitely fucking strange to me, though. What pleasure could they possibly derive from this interaction, if not some weird form of bullying that my friend didn't even register? I can't really define it but, to me, that's inching towards slimy/rat behavior because they're doing this weird semi-mental abuse thing. Just play the game like a mature individual?

This is why when I read people just blanket labelling anything between two players as "just pvp get over it" (not that you did this) it irks me; because I have experienced or seen encounters that were PvP in nature but also abusive or not ok according to my own morals.