markvi was a fun little experiment, and it served its purpose. But the product I wanted to build, it turns out, already exists. There are a lot of in-browser Markdown editors, of course, but there's also a really good desktop Markdown editor with almost the same layout, great themes, and togglable vim keybinds.
I highly suggesting checking out Haroopad if you need a dedicated desktop Markdown editor. It does everything I meant to do with markvi (and 'ayuba' as well), and it's faster and smoother than my app was.
simple markdown editor in angular with realtime preview
based on codemirror
using the always-fantastic marked parser by @chjj
oh, and it's got vi keybinds.