[chousuke]

Ctrl-K is just what came to mind. I think it works in both nano and emacs, and the mnemonic is "kill"

Emacs is without a doubt superior technology when compared to vim. There are perfectly usable vi clones that run on Emacs, after all. The main benefit vi has over emacs is that it's everywhere (except windows :() in some form, so even on a completely unfamiliar machine away from your highly developed dotfiles, your muscle memory still works to an extent.

The main reason I don't use an Emacs implementation of vi is that muscle memory is really bothersome to retrain, and the differences are enough to disrupt my workflow rather badly when using eg. Spacemacs. I just haven't found the benefits to be significant enough to outweigh the inconvenience of retraining myself.