The page has an interesting bug with some special characters... it will initially accept it, showing it in a different font, and then it will change to an empty

The page has an interesting bug with some special characters... it will initially accept it, showing it in a different font, and then it will change to an empty box. I tried a few, such as ™ (trademark) or ∞ (infinity) and they don't show up on the initial overview page, but if you click on the see specimen link you can type the same characters and see that the font does have them defined.