If found a paper years ago that was also looking into the readability of different style choices - how easy is it to miss a leading underscore in _field because

If found a paper years ago that was also looking into the readability of different style choices - how easy is it to miss a leading underscore in _field because it is almost a space or to confuse foo_bar and foo bar and other similar stuff mostly related to casing and spacing. I have been trying to find this paper again from time to time for years now without success, is by chance someone aware of it? One thing I remember in more detail is that it was looking at the bounding box shape and how similar they are, it had figures with different styles and bounding boxes drawn around characters and words.