>the Left text editor running in Uxn (with SDL!) still uses less energy than Emacs does, despite the interpretation overhead
This would work better if your example text editor wasn't an operating system. Does it use less energy than vi?
I'm no expert in Emacs stuff, but AIUI the main selling point is Emacs Lisp's decades of packages, which is both amazingly valuable and also a huge blocker on optimisation, because nobody is willing to break compatibility with all the old packages in the name of performance.
This would work better if your example text editor wasn't an operating system. Does it use less energy than vi?
I'm no expert in Emacs stuff, but AIUI the main selling point is Emacs Lisp's decades of packages, which is both amazingly valuable and also a huge blocker on optimisation, because nobody is willing to break compatibility with all the old packages in the name of performance.