AFAIK, there's no change in the rules for this (and if there is, why then should a PoF be resisted?)
I recall when I proposed that constant enchantments be considered natural (and thus a constantly inflamed sword would bypass MR), and marko prefered not to alter the rules.
There:
General Table Talk - #1641 by Marko_Markoko (which also answers your question, since it was a discussion about MR)
and
Cédar of Merinita - #9 by Marko_Markoko