I learned MacLisp on Multics Emacs back in the late 1970s, and have used various Emacs editors on and off for 45 years.
Now I build Emacs tools to shorten/automate the distance between having a software idea in my mind, and having Emacs implement as much of it as possible. I've wanted to work on advanced Emacs tooling for decades, and now do it in my retirement.
I've been interested in extensible editing environments and software productivity for 45 years. I founded Codefast.com, and spent 25 years building an Internet-scalable, knowledge-based, software build and automation system (1M LOC or so). We reached six-sigma error rates (< 3.4 failures per million builds) by removing humans entirely from the build process. All makefiles for every custom thing imaginable were generated and executed on the fly (1000+/day), on 20 platforms, back in the heyday.