Oh that's an hard topic !

I don't RP-pvp since a very long time but actually, from my little experience i tend to agree 100% with Mishka.
1 - I am a current PS player, i know the races and their flaws/bonuses, the habits of the community. Therefor i have a character that fit in the lore (or tries to).
In that case i just put my char in any situation and RP him/her accordingly to the way he behave, make it a casual talk in a smith area or a fight. A small chat with the opponent in the beginning, giving some info eventually ("OK no magic", "no armor". and so on).
2 - I am a complet new comer and then i don't know anything about PS, the community habits and even maybe nothing about how to RP. In that case i just ask around because i am clueless anyways.
In my opinion, it all depend of the personn you will RP with and that concern all type of RP.
Relying on REAL is not useless because YES in real if someone stab me i will suffer

and try to slap his face! If i actually throw flying rock at you, you can IMAGINE what that could give (toward your char way to be ofc ! )
I don't think the point is there. Making RULES could work if they are very basical else it will be a mess to make everyone agree upon them.
I just think we shouldn't be so ""seriously detailed"" about the mechanism behind an RP... and just start it.
You arrive in a situation where you might come up to a good RP-pvp with someone ? Well just go for it and act like your char WOULD and that's about it ?
If someone godmodd you then just /tell and here we come maybe.