If you're using a browser like Lynx then Epicyon is already quite straightforward to operate via a keyboard. But in a more conventional browser, like Firefox, it wasn't so easy to use with keyboard only. Not until now.
Keyboard shortcuts are now supported so that you can navigate around, make posts and search. You can also change them as needed. Shift + Alt + k opens the keyboard shortcuts screen, you can go to the DMs timeline with Shift + Alt + d, and so on. Once you know the keys then moving between timelines, calendar or search is very fast.
Operating web sites only with the keyboard is a minority thing, but it will be useful for some scenarios. It would also allow for the system to be operated using unconventional input devices.