In reply to wout:
It all depends on the shape/fit of your foot in the chosen boot.
So foot, sock combo, boot - all need to be looked at together as one system.
You can't change the shape of your foot, only your socks or boots.
Your foot takes up volume in the boot. Your socks also take up volume in the boot.
multiple layers of socks may make your feet colder as they take up more space and may stop you being able to wiggle your toes to keep them warm.
I returned a pair of lorpen expedition socks becuase with my foot/boot combo I was convinced they took up too much room in the toe box and I would be getting cold feet.
On Denali I used Phantom 6000 boots and when I bought these a few years prior, I made sure there was enough room in the toe box to be able to wiggle my toes. The problem with this was that it introduced a tiny amount of heel lift - I chose to live with this as a trade off for having better toe wiggle'ability.
I then went through a process of testing heel wedges, volume reducers in strategic places, lacing tightness etc to get rid of the heel lift and get the best possible fit.
The last thing I tried was merino liner socks under a pair of heavy tight knit wool socks. Worked brilliant and I could ditch the heel wedges and never had any blisters foot problems.
So it all depends on the boot, foot, sock combination.
Post edited at 15:06