I think it is. Along with the "A list apart" header on the top that is partially obscured by the fixed navigation pane and the title being too wide for the page.
I think it's because of lines like this: <code>navigator.windowControlsOverlay.getBoundingClientRect()</code>
They need word-wrap: break-word; on there or something.
I've seen other sites do the partially off-screen site name thing but not making the name fit the width of smaller viewports is odd.