Well, I have no idea what Roland is arguing here, but let me address the part about using rarity as a balancing factor...
I believe I mentioned that it was rare once, and it was in listed along with several other things that actually are balancing factors. Rarity was not ment to be an important part of the equation, simply a little add-on which doesn't really mean anything, because the fact is that adamantine is not unbalanced in the slightest, and furthermore would be incredibly weak if it couldn't bypass DR.
I believe I mentioned that it was rare once, and it was in listed along with several other things that actually are balancing factors. Rarity was not ment to be an important part of the equation, simply a little add-on which doesn't really mean anything, because the fact is that adamantine is not unbalanced in the slightest, and furthermore would be incredibly weak if it couldn't bypass DR.