It's because of some bad offset between background and text... Exactly, the issue is at: text-underline-position: under; (also 'from-font' would break it.)

It's because of some bad offset between background and text... Exactly, the issue is at: text-underline-position: under; (also 'from-font' would break it.) It's clearly not intentional - it's a glitch, probably in the font.