Brian, I'm siding with you. I think a lot of "condensation" problems with down bags is due to a general lack of awareness about how to use and handle down. Its easy to find fault, harder to gain the experience to avoid problems.

Basically Andy's question was this
1) can a breathable non-water proof bag be made significantly more waterproof by spraying a DWR on it, and would that help in a tent from occasional splashes - well sort of maybe. I think its worth a try. To those who say it will have more condensation problems after application of a DWR, I say BS... a bivy will have far worse condensation.

2) Is it a good idea to have a sort of water proof shell on a down bag inside a tent? - I say yes, others say no. Personally I do not have condensation problems with my down where I go and how I use it. Also goretex works perfectly for me and I have 30 year old goretex jackets that work nearly as good as new, and I have a goretex bag and a [I think its drylight] bag, and I love both of them.

soap box on:

HOWEVER question "common sense" and "camping trends" because they rarely are based on deep experience, but rather on first order physics. For instance people will say titanium pots are poor conductors because titanium has a lower conductivity coefficient, but what they totally ignore is the laws of thermodynamics and don't realise they must divide the coefficient by the thickness, and titanium is made thinner and actually titanium pots conduct better than thicker steel ones. If you set a stainless steel pot and a titanium pot same size on snow and pour boiling water in them, the water in the titanium pot will cool much more quickly.

I mean the condensation arguement completely ignores that water is a three phased material that can pass directly from any phase to any other. Ice can evaporate without first melting, and vapor can freeze without first liquifying.

and finally - Some of the most experienced influential outdoorsmen are total crackpots.

soapbox off

Jim