The rules actually aren't
that complicated to think about. You only have to think about 1/3 of the text of the RDM rule at any given time, and those thirds are mostly examples and specific circumstances. If you meet those circumstances, which are easy to memorize, you can kill. Simple.
I don't care much about someone's motives for attacking someone. I'd ask my friends to design a system in which you spawn in the brig every time you join so you can't repeat the same behavior - exactly as how CityRPs handle it.
And there would be a rule against intentionally trolling/only joining to try and make others miserable. So if you did continually do it enough you would get banned - not because you randomly attacked me or had no motive - but because it became clear through your actions that your main motive on the server is to troll.
In what way is that a fair comparison? I've played other RP servers before (BluZone, Comr4de's, Flareon's, etc). I've hosted my own RPs years back as well. I had very few complaints about anything.
Even if after enough times you ban somebody for joining solely to troll (such as Tony), in our server, the damage would have already been done, because characters in this server die permanently.