“Over the decades I’ve only had one incident where my down sleeping bag became too wet over a period of nights that put me in a potentially dangerous situation”
This is precisely what I wish BPL had more field data on – just how how WP down performs while on extended cold/shoulder season use. While I suppose most users of down protect it from bulk water issues, dealing with gradual moisture buildup is far more tricky to manage.
In theory, I’d wager that wp down should improve vapor management, since the down plumes are (allegedly) more hydrophobic than their non treated counterparts.
Regardless of what WM says about “natural oils” on down, we all know what happens to down when it gets wet, natural oils or otherwise. And down loft loss is a very common issue on extended cold/damp weather trips, when not properly tended to. This is a proven fact.
Which is why folks either use synthetic or bring a second “outer bag” to handle the moisture. But if we had more field data on WP down, it could be pretty helpful, imho.