Hardhats originally were developed to protect a person's head from falling rivets and other small objects that could injure an unprotected head.
Today, hardhats also provide protection from electrical shock. They do this partly by creating a distance between your face and the source, via the bill of the hat. Wearing the hat backwards defeats this safety feature. And they do this partly by presenting a nonconductive barrier between your head and the source. You can defeat this safety feature through gratuitous use of conducting stickers, ink, and other materials.
Stickers can also weaken the shell, thus reducing impact protection. Storing objects (even paper) in the space between the shell and the suspension reduces the air cushion between the shell and your skull. Don't modify the hardhat.
Do you need to wear your hardhat when entering and exiting work areas? What about breaks and lunch? Electrical hazards and airborne objects don't “know” whether you're on the clock or in your assigned work area. If you're in a hardhat area, wear your hardhat. A hardhat can protect you only when you're wearing it. Any area at your facility that isn't specifically designated as not being a hardhat area is a hardhat area.