Some silliness going on here. OK, it's clear, he can look through it and see his students reactions as he writes, OK. The writing is backwards so no one can read it direct, it is shown by camera flipped. Then there's no point in all the extra stuff to make the lines fluoresce since it is unreadable unaltered anyway. He just needed a clear touch surface, which is common anyway since we slap them on top of LCDs in countless products. Making the unreadable lines bright is actually a disadvantage, since they are unreadable and they are blocking the sight between the parties.
From TFA, this is just a means to produce nice looking videos to teach his lessons.
His students watch the videos at home, then the classroom time is for doing the homework with the teacher available for firsthand assistance. That is the flip teaching described in the article, which is being confused with the reversed-screen being shown in the picture.
