Originally Posted by Ironfish653

Probably won't damage the shoes, but if the 'platform' of the pedal is wearing down, or if you have damage to the plastic cleats (common from too much walking), then they will not sit flat, and may cause your foot to rotate ever-so-slightly in a way you don't want it to.

Most (all) clipless-compatible shoes have either a plastic or carbonfiber insert. My road shoes don't even have an outsole, just a little rubber pad at the heel, and bare, shiny CF on the bottom. My Pear Izumi's look like chunky running shoes, and have a plastic insert running from the just after the toes to the heel. There's a lot of cushion under the heel, so you can walk normally on it, and the toes flex a little, but about as much as my work boots.