but that goal could still be accomplished in a native application that embedded a JS runtime for plugins. The easy-to-hack bit is not about the specific script

but that goal could still be accomplished in a native application that embedded a JS runtime for plugins. The easy-to-hack bit is not about the specific scripting language but about the UI being completely hackable. No other editor (except emacs) lets you hack the interface as well as Atom. And any attempt at exposing enough hooks to allow a native text editor UI to be as hackable would, in a kind of Greespun's 10th rule, probably result in a bug ridden, poor implementation of an HTML engine.