had to disable vimium because it doesn't work well with this site. I don't know enough about the extension to know whether that's the site's fault, but I'm assuming it's not a blacklist type of thing. Improving accessibility might solve it

Because you don't have an input text area focussed, vimium will assume by 'j' you want to scroll down for example, because that's the point of it. Iirc you can manually enter insert mode and then it should work fine.