Ah, the font reader uses the pixel at 0,0 (the top left corner) to determine what the background color is for the rest of the font bitmap (because technically bitmaps can use either a black or white background color as desired by the creator), so the problem here is that first character actually uses the upper leftmost pixel. That pixel must be black to detect fonts correctly.
I'll add that bit to the manual.
Edit: If you like I could also add a cfg option to override this setting. It's nice that it's usually handled automagically, but sometimes there are special circumstances like this font.