https://wccftech.com/apple-warns-users-against-closing-macbooks-with-a-camera-cover-to-prevent-display-damage/

Apple posted a support document in which it warns users that closing their MacBooks with a camera cover can damage the display. While some laptop manufacturers integrate a kill-switch for the front-facing camera, Apple warns users to not put a camera cover. Usually, Mac users apply stickers or tapes on the front-facing camera to prevent spyware from snooping.

In the support document, Apple warns users against using a cover over the camera as it might lead to display damage. This happens when you close the lid. In addition to this, the auto-brightness feature on the MacBook is also affected when you cover the camera with a cover of any kind. True Tone settings also take advantage of observing the color temperature of your surroundings and applying covers over the camera just interferes with the process.