Meanwhile, at the other extreme, in many proportional fonts the widths of letters vary so characteristically that clever readers can decode a text mostly just f

Meanwhile, at the other extreme, in many proportional fonts the widths of letters vary so characteristically that clever readers can decode a text mostly just from the widths: see Donald Knuth's "N-ciphered texts": https://digitalcommons.butler.edu/cgi/viewcontent.cgi?article=3283&context=wordways https://digitalcommons.butler.edu/cgi/viewcontent.cgi?articl... (Not linking the solutions here to make it harder to spoil the puzzle, but you can find them online with a bit of effort — maybe this will help: https://digitalcommons.butler.edu/cgi/viewcontent.cgi?article=3283&context=wordways https://digitalcommons.butler.edu/cgi/viewcontent.cgi?articl... — and it's also reprinted in Selected Papers on Fun and Games.)