Good timing for us, given our emphasis on typography and readability: the new, updated Quality Matters 6th edition — the one of the primary standards for reviewing online courses — includes an increased emphasis on Readability, both for review and for scoring:
“Readability can be defined not on a letter-by-letter basis, but by how the combinations of letters are read within a larger body of text. In other words, readability is defined by how easy it is to read words, phrases, or blocks of copy such as a book, a web page, or an article.” (Web Typography Overview)