Bare Metal (The Emacs Essay)

To me the charming thing about Emacs is how introspective a program it is. This goes beyond all the documentation being built-in, and being able to redefine things on the fly. For instance, it's easy to define a keybinding that does "Take me to the source code of the command that's bound to the next keybinding I type". When you use that and land at a destination, it will probably be Elisp code, but in some cases will even be C code - it works either way.

I have never once thought Visual Studio needs some way to edit its own source code on the fly... whats the actual use case?

Good question, you may have to be the ultimate power user to need this feature? What are those people doing?