Some teachers think that basing 20-30% of the grade on grammatical and stylistic matters is unfair unless they mark all the flaws. We approach this issue from the perspective of readers. If I review a textbook and find editing mistakes, I don't label each one and send the text back to the publisher. No, I just stop reading and don't adopt the textbook. Readers who are not teachers just don't keep reading if a text is too confusing or if errors are too distracting. Readers who are teachers are perfectly justified in simply noting with an X in the margin where a sentence gets too confusing or where mistaken punctuation leads the reader astray. Students are resourceful (they can get help from our on-campus Writing Center or Writing@CSU) and will figure out the problem once a reader points out where the text stumbles. That's really all it takes.