Yagoda wrote the book, The Sound on the Page: Style and Voice in Writing so he knows from commas. ICE, an acronym he suggests may help you avoid the error in this sentence.
Yagoda began teaching at the University of Delaware, "some years ago." He's been "positively gobsmacked by the multitude of comma splices" he's confronted there, they haven't abated. Sounds more like negatively gobsmacked, to me.
Next week we'll practice removing diseased :s.