You may want to consider mobile-friendliness purely client side, using CSS to set up different layouts depending on the resolution - what's typically called Responsive Web Design. Sounds cumbersome, but with just the right couple of design tweaks you may get 90% usability on mobile.
Actually, I think the issue here now that I think of it is that we do media query detection in on the React side to figure out which components to render. Really, we should just render a single component and have CSS to cover both cases.
Other sites do this, so it should be possible, though it would require me to change the react component that renders the sidebar (I'm using Atlaskit, but that doesn't have support for mobile responsive rendering, sadly).
