OK, I'm back. So, about Demostix's question:
So, do any regular users of VBs have to make an exception for their feet? BillyBob?
Like you, I sweat in Crocs every time, which I mostly wear without socks. But this has not caused me problems in using VB socks, which is the main form of VBs which I have used, on and off since the early 80s. I learned about VBs from Patagonia catalogs from that era. Back in those days they did not make any breathable rain gear at all.
And it is not that my feet never get wet using these VB socks, because they do, even if more sometimes than others. But it is still warm, and keeps the footbox of my TQ dry. There have been times when I was very aware of the wetness. The first time or two it really freaked me out, because when I felt the wet my subconscious probably screamed " look out, cold feet and wet insulation is right at the door!". But the cold never appeared, in fact I was probably always noticeably warmer than without, although sometimes with an unpleasant wet sensation. I learned to ignore it if I was in need of the VB effect.
About the wet socks and Croc lining: in the case of VB liner sock or clothing ( or maybe bare skin ) it is sacrificed to the wet. That is why it is thin a layer as I can find. It's primary purpose is to reduce the unpleasant sensation of wet coated waterproof fabric on my skin. But some times, especially feet, this layer gets wet and I just ignore it. ( but no layer used with my current VB socks which are lined with "fuzzy stuff".
I have not noticed being wet or even damp wearing my VB shirt lined with fuzzy stuff except one day doing yard work and going up and down stairs into the attic. Sitting around at room temp or wearing the shirt under a Packa rain gear while walking as fast as possible in a cold rain, no sweat noticed.
About this last time in my HHSS and my feet were feeling clammy inside the footbox even without a VB, just nylon socks then not much worse when I put the VB socks on: makes me think about the time the Backpackinglight folks had a lot of trouble with the footbox ( and only FB ) of their down bags collapsing. With no exposure to external moisture. It also makes me think of the time the foot of my bag and foot of the HH pad ( and no where else ) were soaked with condensation the time I did not use the space blanket. Do the feet put out more moisture ( either sweat or vapor ) , even when it is cold, than the rest of our bodies? Does this account for a lot of the cold feet people get with thick wool socks and several inches of down around their feet? Due to all of this evaporative cooling in the feet plus that moisture getting into the down? If so, would a VB sock stop all of this, even if it gave you wet feet under the VB?