The comment was well within the guidelines and is a viable point. When people make broad statements on Lisp like the original great-grandparent comment, they really need to clarify whether they're talking about Common Lisp or Lisp-likes. The original LISP doesn't have the features that Common Lisp has, so it'd be weird indeed to say that LISP wasn't an actual Lisp.
In retrospect, the comment was talking about Common Lisp and not just Lisp-likes and tried to make the distinction but did a poor job of it with comments like:
> Clojure and Racket are in that category. They lack the full power of CL; so they're just Lisp-syntax languages, not an actual Lisp.
Common Lisp and/or its implementations (and a bunch of other dialects) have most most of the features of the original LISP directly, often with minor changes, like many of its operators and data structures (like the linked list). It was designed to be largely backwards compatible with earlier LISP. Original LISP implementation features like the self hosting machine code compiler, loading of natively compiled code and the ability to save/restore images of the Lisp heap (which really was already in the 1960s LISP) are also provided by various later Lisp implementations, incl. several CL implementations.
In retrospect, the comment was talking about Common Lisp and not just Lisp-likes and tried to make the distinction but did a poor job of it with comments like:
> Clojure and Racket are in that category. They lack the full power of CL; so they're just Lisp-syntax languages, not an actual Lisp.