I thought I read something similar in Levy's book "Hackers" but the following is from https://www.gnu.org/gnu/rms-lisp.en.html

"It was Bernie Greenberg, who discovered that it was [2]. He wrote a version of Emacs in Multics MacLisp, and he wrote his commands in MacLisp in a straightforward fashion. The editor itself was written entirely in Lisp. Multics Emacs proved to be a great success—programming new editing commands was so convenient that even the secretaries in his office started learning how to use it. They used a manual someone had written which showed how to extend Emacs, but didn't say it was a programming. So the secretaries, who believed they couldn't do programming, weren't scared off. They read the manual, discovered they could do useful things and they learned to program."