OK, thanks for looking into it
If it's just cosmetic, I'll just switch to a working font. I don't actually read in the viewer anyway; I use it to see if everything is in order after I edited a book. I can do it faster there than in the editor itself.
Weird bug though... But then again, I'm not a font rendering expert.
Don't you sometimes hate (developing) software? Be honest, sometimes you do

I know I sometimes wish the computer was never invented