I live in, and was raised in, Michigan,USA. From 6-12 grade I walked to and from school every day. About 2.567 miles each way in winter snow, up hill both ways! My feet were always cold in the winter outdoors. Well, anyway I frequently developed hardened heels and then they would crack, occassionally bleed but always hurt when I walked on them. And take forever to heal. This would happen in the summer if I wore sandels. I came to believe that if I kept my feet warm/moist with socks and footwear the cracking would almost disappear. Much more pleasant life. So I found the above referenced article very interesting.
I am now living again in Michigan but the winters seem warmer than before, I rarely walk outside, and other than when sleeping, wear shoes and socks. So cracking has not been an issue. However, I am new to Karate and will watch from cracking in the winter from now on, especially in the Dojo. I don't want to contract any illness through cracked heels, nor pass anything on to others. There is one student who wears white shoes in the Dojo. It does not seem to be an issue. Have seen "Katate Shoes" for sale on the internet. Also, there are several students who wear an elastic wrap on their hands or feet.
I certaintly hope it does not become an issue for me.