Hi Ken,
They are all Sphagnum mosses but the one being referred to in this forum grows in bogs, mostly in Canada. The top layer of living moss is scraped away and the decomposing moss underneath is mined and processed for use in potting soil (but you know all that).
The controversy is that some believe this a is non-renewable resource that is home to many different species of plants and animals, some endangered. Others contend that the bogs are renewable and there are so many peat bogs all over the world that it doesn't matter if we dig up a few.
The carnivorous plants don't seem to mind which moss you use (milled, long fibered....), as long as its the bog type. The biggest problem, as Tarev points out, is finding some that isn't fortified.
Daisy
