Honestly, I just read through the few rules for this site and the only thing I found mentioned about pm's is that you can't solicit sales through them. Apparently everything else is a go through pm's and only the ethics of proper forum etiquette are suggested to be practiced in pm's. If he asked about a source, it is ok unless it was attempted to sell something in the pm.
Please someone correct me if this is wrong since I am still fairly new here.
@bickel29 you seem well versed in the written as well as the unwritten rules of this board.
Edit: shit storms sure can get confusing