This version fails for numbers like 5, showing "5. Buzz". In the case of a number divisible by 5 but not 3 nothing prevents the 5 in the ::marker from rendering.

Edit: it looks like your version can be fixed into a working 85:

  :nth-child(5n){list-style:'';&:after{content:"Buzz"}}:nth-child(3n){list-style:"Fizz"