I hope that commenter was being hyperbolic. I have heard of headphones making visible impressions or “dents” in the soft tissue and msucle after long periods of use (Google Tyler1 headphone dent if you don’t believe me), but such a dent would disappear within minutes or hours. An actual deformation of the skull due to headphone-wearing would definitely be strange.
at no point should your skull be deforming. Maybe the skin and fat layer ontop but the skull itself should not be deforming after an hour of hearing a device on a healthy individual.