That is indeed useful information, but in all fairness, finding that a garment will eventually be wetted through while in use in constant rain is not representative of the way in which a down sleeping bag is likely to be used.

I did have an interesting night during which I slept out in a down bag (standard untreated down and nylon) inside a bivvy bag during a night of alternating rain, fog, and snow. I sensed that the loft of the bag was decreasing, although dawn arrived before it got to be really bad. My take on the situation was that I would have been warmer if the temperatures were cold enough that I only would have experienced snow.

In cold, rainy conditions I really like synthetic fleece for outerwear, especially underneath a shell garment. I can then anticipate a warm night in my dry bag, waiting for me back in camp.