You appear to consider "Emacs" and "GNU Emacs" synonymous. I explicitly do not. Hemlock is not a reimplementation of GNU Emacs; it's derived from earlier Emacs

You appear to consider "Emacs" and "GNU Emacs" synonymous. I explicitly do not. Hemlock is not a reimplementation of GNU Emacs; it's derived from earlier Emacsen, just as GNU Emacs is. Hemlock in particular is based on ZWEI, and was in version 0.99 around the time that work started on the GNU Emacs project. It's a slightly older sibling of GNU Emacs, rather than a descendant of it. GNU Emacs has undoubtedly become the de facto standard Emacs, but I don't see why that disqualifies other branches of the Emacs family tree from using the name that all of them inherit from the venerable TECO implementation. My point was that Emacsen have already been built in Common Lisp, but that they do not serve as substitutes for GNU Emacs--a point with which you appear to agree. Maybe we even agree on the reason why: because no Emacs implementation can substitute for GNU Emacs without supporting its ecosystem. The amount of work needed to do that would be enormous, whether the proposed substitute is written in Common Lisp or in something else.