I have friend who went to culinary school who claims that cold eggs crack cleaner than eggs at room temperature.  Do egg shells crack cleaner coming cold out of the fridge?    Does warming up to room temperature for a few minutes cause the eggs to crack less clean? 
Aside from technique (always on a flat surface, never on a knife or bowl edge) the age and temperature affect the cracking due to moisture and elasticity.   As eggs age the membrane separates from the shell which leads to smaller bits being able to fall away.   An egg which is fully at room temp, which is more than a few minutes, will have more elasticity to its membrane. This will worsen shell chip loss for older eggs. For decently fresh eggs it will not matter.   Bottom line if your eggs are fresh and you crack correctly temp does not matter.   Incidentally if your eggs have a flat spot when hard boiled they are quite old or have been stored improperly.  