Skimming this thread, while quite fascinating, is also quite disheartening.
It is sad to see people so wrapped up in the peddling of polycentric law bullshit, and those who oppose it, that it loses sight of the FAR MORE IMPORTANT issue. That being, ethics and morality.
I used to be (and am still), an advocate and believer in the polycentric law model, but to see what is going on here, with the petty bickering over things which really are of no moral consequence at all, is sad. The thread has simply devolved int utilitarian bickering. The only people who can find any "meaning" in such conversations are self-admitted utilitarians or latent-utilitarians.
When I see this kind of thing, I know the useful portion of the conversation has pretty much come to an end, and one or more parties should just end it right there... because the moral argument has simply ended at this point, and when that happens, I think the conversation need to be over, as it has devolved into an empty shell of a debate.
What happens when people of differing systems of belief (or different competing agencies) come into conflict?
If you think that kind of conflict is a "bad" thing, in a deontological sense, then I suggest whomever believes that needs to completely reevalute their entire understanding and belief in ethics and morality, because only a strict-pacifist or nihilist has any business asking that kind of question.
Competing systems of belief have existed since time immemorial, and that shall continue to be an objective fact until the end of time, and these conflicts exist throughout the universe. There is nothing you can do about ending this conflict, nor is their anything inherently wrong with that fact to anyone other than a nihilist.
Polycentric law is designed to minimize these conflicts, not eliminate them entirely. Entirely eliminating conflict between competing systems of beliefs is a mathematical impossiblity.
If this means people will fight. So be it. If this means people will die. So be it. It is not a bad thing, and if you think death or harm and fighting over what you believe is morally right is a "bad thing," such people need to reject morality entirely, and go jump on the nihilist choo-choo train.
Addendum - just going to add in a postscript comment. Whether the phrase, "bad thing," in this last paragraph was the best choice or words, I don't know... it might have been best to simply say that conflict is inevitable when people disagree on ethical fundamentals (first principles,etc...). Obviously fighting is [arguably] bad in the sense that few people actually want to fight or be killed, but I meant it is not a bad thing in the context of defending what you feel is right should not be considered a bad thing, else the whole point of ethics and morality becomes a moot point.