I don't doubt what you're saying Evan, but I kind of doubt what you read. The green raw sphagnum's high acidity levels would seem to make it an undesirable host environment and quite immune to biological attack. I'm not 100% sure about that, though.
As far as I know, the dried and processed raw sphagnum is not treated with chemicals of any kind. We have a major producer, processor called Mosser Lee here in Wisconsin. The plant and drying operation is easily viewed from any of several roads close by. The drying operation technique appears quite ancient from what you would expect to see in this day and age. It is done exactly the same way as coir (coconut fiber) is dried and processed in India today. If you use your imagination, you get the picture. The gathered moss is spread out over large, very clean sandy fields in open air to sun dry. It gets washed by the rain and dried by the sun several times with repeated tufting and turning in between. After several cycles of this, the dried clean moss is brought inside and cut or milled (Damp-Off) and packaged as you see in stores and garden centers. As far as being clean, it does have a few occasional grass seeds occluded and it always contains a few small dried sticks and stems which can be a source of irritation when preparing media for seeding; but a 'small price to pay' for all the goodness it does.
