It's one of the sentences which creates endless confusions and a false image of Lisp. 'Everything is a list'. Oh, Lisp has only one data structure? Lisp is difficult to read, because it has no other syntax? Lisp is a primitive language and not usable for real programmers... etc. etc. It also creates the impression that even proponents of Lisp-like languages don't actually understand the basics...
Who is endlessly confused? Who suspects that the author of a neat lisp editor plugin has never written a non-trivial line of Common Lisp, Clojure, or Scheme? What are the chances that people in either category are also curious and excited to experiment with novel editing techniques?
If we're going to be super pedantic, the Common Lisp spec actually defines code as:
"code n. 1. Trad. any representation of actions to be performed, whether conceptual or as an actual object, such as forms, lambda expressions, objects of type function, text in a source file, or instruction sequences in a compiled file. This is a generic term; the specific nature of the representation depends on its context. "