Having a WiFi connection set to public makes it more secure than when set to home.
However, I am wondering if this might be something related to your display driver and specifically how it handles text. If you happen to have a monitor you could hook up to the laptop that might help to determine if that's the problem if a mirrored display works fine on the external monitor but not on the laptop's own.
One thing I would definitely do is check at your computer manufacturer's support site for the model you have whether there are any recent updates for the display driver for your machine. If so, I'd look in device manager to see what's currently shown as your driver.
Have you applied any recent Windows Updates that might have tweaked your display driver? If so you could try going back to a restore point prior to the last update, see if the issue is resolved, and keep trying this cyclically until you either stop seeing this issue or know that you're back as far as you can go in order to test this out.
Brian AKA Bri the Tech Guy (website in my user profile) - Windows 10 Home, 64-Bit, Version 1803, Build 17134
. . . the presumption of innocence, while essential in the legal realm, does not mean the elimination of common sense outside it. The willing suspension of disbelief has its limits, or should.
~ Ruth Marcus, November 10, 2017, in Washington Post article, Bannon is right: It’s no coincidence The Post broke the Moore story