Yeah, I got to the following line and stopped reading:

First, this code assumes that (if (null list1)) in Common Lisp will be equivalent to (if (nil? list1)) in Clojure, but Clojure doesn't consider an empty list to have a nil value.

That sentence makes it very clear the writer either hasn't been arsed to read through even one Clojure tutorial or is being intentionally dense. If they have an educated opinion, great, but I have no patience for this level of ignorance, especially if it's feigned ignorance.