In a new support document, Apple says not to close your MacBook’s lid while using a webcam cover. Doing so can damage the screen.
Webcam Covers
When you close your MacBook’s lid, the space between the screen and keyboard is small, and the added thickness of a webcam cover could damage the screen over time. If your cover is thicker than 0.1mm (average thickness of printer paper), remove it before closing the lid.
Apple’s advice is to control camera access in System Preferences, and the camera indicator light to figure out if the camera is active. Mac cameras are designed in a way that it can’t activate without the green indicator light also turning on.
Read more at MacObserver.com