The author mentions the loss of vim-like web browser controls when the Pentadactyl extension didn't convert over to the webextensions api.

You get the vim functionality back with the following extensions:

Firefox -- Vim Vixen (https://addons.mozilla.org/en-US/firefox/addon/vim-vixen/)

Chrome -- cVim (https://chrome.google.com/webstore/detail/cvim/ihlenndgcmojh...)