But the construction of MacBooks can make it dangerous to install accessories on the keyboard, palm rests, and display. There’s a small amount of space between the top and bottom casing of a MacBook when it closes, so placing something in between could cause a problem when closing the laptop.
Anything left inside the MacBook — from a large crumb to a camera cover — can potentially break the screen when it closes. However, Apple does sell privacy screen protectors on its official Apple Store website. That would insinuate that there’s no risk of a privacy screen protector inadvertently cracking the MacBook’s display.
What Apple Says About Other Accessories