system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why some of my hard-boiled eggs are nearly impossible to de-shell, while others take hardly any effort.
gpt
Fresh eggs have shells which are more porous and stick to the inner egg when boiled. Less fresh eggs develop a small amount of gas which, when you boil it, separates the egg from the shell like a little bubble. The shell becomes less porous over time. The result is that the eggs become easier to peel after boiling. 

N.B.: Regardless of the freshness factor, putting a spoonful of baking soda in the water when you boil your eggs should make them easier to peel, too.
Source: sister keeps chickens for their eggs.