On a real cold day there is probably ice in the bottom that can be seperated from the liquid gasoline. The ethanol if present will make water much more soluble in gasoline and the ice tactic might not work well.If you accidentally shook the gas can, and took the cap off on a hot, dry day all of your hard work would evaporate off. If the gas can is not sealed up, and it goes through a lot of the heating up and cooling down cycles, the amount of water would increase more rapidly. That's a good reason to not leave the can vented to the open air during the winter.
Wouldn't the vapor pressure of the gasoline be more than the vapor pressure of the water in this scenario. It has been a while since I reviewed how the partial pressures would apply.
I am kind of with post 12 sorry to hear your Stihl ms170 is way more problematic than the Husqvarna 36 I start and use a little perhaps once a year and change out the gas every year or two.