Several of these topics have been covered by people far more experienced than myself, but I thought i'd add my opinion.
PvP: The reason that I have gone years without free-form rp. In my experience, free-form rp is usually useless and frustrating. I've never met a player who was mature enough not to god-mod, and when PvP became popular on a site then no character was safe.
Having said that, this site is much, much different than any other 'free-form' type roleplay site i've seen. While writing skill does not necessarily equate to maturity, I think the format of this website discourages the participation of immature players and godmodders in general. (Of course, I do have say that discouraging is not the same as prohibiting entirely).
I think that if we want to have a good player versus player experience for all involved we should include some or all of the following:
Players should always have the option of asking for a moderator, and pausing the scene until a moderator is available. Let's face it, we don't always want to kill our best friends. Occasionally our character will piss off the character of someone that we only have passing familiarity with, and when you barely know someone you aren't exactly qualified to decide the fate of their 'baby' (as someone wisely put it) with impartiality.
A chat wide standard. Many will probably disagree with me on this one. Writers are artists, and nothing ******* off an artist more than limitations they dont agree with. Having said that I think that a general website standard for pvp is just as important as the standards for normal posting. Something I would suggest we include in this standard is the idea that you do not post the strike, but the attempt. Many other things could be put forward in the development thread, but I think it should be simple and not cumbersome. Easier said than done, which is why it would be best left to the minds of multiple players debating the pros and cons in development.
And finally I agree with Miharu Mindi in the statement that our actions should have consequences. I do want to take it a step further. It should be made clear that our actions have consequences in the wide world. At least until the current crop of 'toddler' characters become characters of epic scope and significance, a heavily pvp focused character should spend all of his 'killing free' time in fear of discovery.
Think about what would happen in this world if you killed ten, five, or even three players in two months. Soon, you wouldn't just be fighting players. The authorities would have descriptions of your character if you were careless, if you were blatant in your slaughter they might even have sketches. Criminals might flock to your banner (as was stated, i think, by the man with the unpronounceable name), and players (along with their npc friends and allies) would surely flock to oppose you.
You would have to be a powerful character indeed if you even wanted to avoid being on the run after such episodes. Even in a violent post-apocalyptic world, if you base your character around the killing of other people you will become a polarizing force. We don't want to discourage people from doing it, we don't want to force npc or player reactions, but we do want to maintain continuity within the story and the reactions of all the characters in our world when someone goes on a killing spree.