Seems like the conceptual design helped with that too, reducing the activation energy needed for clear, interactive documentation. The code and the UI are both designed against the same set of consistent concepts, which naturally brings them together and, in turn, makes it so much easier to tie them from one to another. Simplest example: every interaction in the UI is a "command" and commands are reflected in elisp, so having a way to jump from an interaction to the corresponding code and documentation just makes sense. The documentation can be organized along the same conceptual lines as the code and the UI.
Seems like the conceptual design helped with that too, reducing the activation energy needed for clear, interactive documentation. The code and the UI are both designed against the same set of consistent concepts, which naturally brings them together and, in turn, makes it so much easier to tie them from one to another. Simplest example: every interaction in the UI is a "command" and commands are reflected in elisp, so having a way to jump from an interaction to the corresponding code and documentation just makes sense. The documentation can be organized along the same conceptual lines as the code and the UI.
Emacs really is an amazing design study.