It's pushing her away from what every other bit of software on her system, including the OS itself, has trained her to do
But that's not true if you're the kind of user that uses VIM regularly, since many CLI (ncurses) programs use the same keys. And even on the web: Gmail, Google Reader, Google+, Reddit, Jira, Tumblr, Tiny Tiny RSS and others support J/K for up/down navigation.
Anyway, adding keyboard navigation directly to a web app (instead of as a browser extension) breaks the "do one thing and do it well" philosophy.
This is why Google Chrome doesn't allow one to use Backspace to go back to the previous page (the most used shortcut for a browser) or Slash to trigger inline search. Instead, you have to use CTRL-Left and CTRL-F, as the one-key shortcuts are reserved for their web apps.
But that's not true if you're the kind of user that uses VIM regularly, since many CLI (ncurses) programs use the same keys. And even on the web: Gmail, Google Reader, Google+, Reddit, Jira, Tumblr, Tiny Tiny RSS and others support J/K for up/down navigation.