A screen protector is a common safeguard for phones, but Engadget advises against using one on a MacBook. The publication argues that laptops are less prone to drops and are closed when transported, so the main benefits are limited. More importantly, the risks outweigh the advantages.
The biggest concern is damage to the anti-reflective coating. When a protector is removed, its adhesive can leave the coating cracked or peeling. A thick glass protector can also bridge the small gap between the screen and keyboard, so closing the lid with force can transfer pressure to the display. Even if a protector is needed, Engadget suggests a thin magnetic option, such as Kensington's UltraThin Magnetic Privacy Screen Filter, which avoids adhesive and thickness issues.
The article also warns about other accessories. Heavy hardshell cases can strain the hinge and trap heat, while keyboard and webcam covers can disrupt the tight tolerance between the screen and base. Apple reportedly recommends removing keyboard covers before closing the laptop and using webcam covers no thicker than a sheet of printer paper.