"Looking for clarification from Dave or another admin."
Mod on. PP is indeed the coin of the realm. Perhaps that should be reconsidered but for now it's the only medium that affords some protection for buyer.
It was not long ago that USD was currency of the realm and some of our Euro members successfully made the argument that Euro should be accepted in Euro transactions.
Mod off. Hypothetically in situation described above - if a listing was for knife, $200, without citing a method of payment, I doubt that by itself would rise to mods level of attention. It would not for this mod. Negotiate in PMs and hopefully the mods will not have to referee.
Mod off 2. Rick, if you're going to sell a knife, pm me first. You know I buy most everything you list.