IDE display broken badly

[supuflounder]

I have the latest (1.8.12) (Windows Store 1.8.33.0). I am getting totally messed-up display. Here is a screen shot of what I see:

But if I copy the line from the IDE and paste it into NotePad++, I see what I expect:

Here is another example. The IDE shows me this

But the copy-and-paste reveals the content is as expected

I could give dozens of examples, including ones where each space is expanded so that the single-space between words looks like six to ten spaces. If I roll the mouse over the line to select a region, the letters flow in weird ways as they attempt to look like what I should see.

The IDE is nearly unusable. I copy the body of a function out, move it to NotePad++, edit it, and replace it back in the IDE, where it is mangled beyond usefulness by the display logic.
I am using Windows 10, here's a screenshot of the "Properties" of "This PC":

The Arduino IDE is the only program that exhibits this pathology. NotePad, NotePad++, Word, this box I'm typing into, do not have this problem.