Normally after standing in powdered snow for a while, the player becomes chilled and their hearts turn blue, slowly losing life. In hardcore, however, the hearts just disappear completely, rather than turning blue, which means that players don't know how much health they are at. I suspect this is because there is no texture for blue hardcore hearts, so the game just drops the texture entirely. The heart texture reverts to normal after exiting the snow. 

Steps to reproduce:

1. Be in hardcore
2. Find powdered snow
3. Sink in the snow until completely chilled; heart texture disappears as soon as the player starts to take damage