Ha, to me it is an improper max width. My biggest peeve with the GitHub web UI is the squished center pane.

I hate that it centers it with giant gutters wasting over half the width of a 4K monitor, should I choose to maximize a browser window. I'd much rather see everything shifted to the left. I'd even be OK with some soft margin still causing regular README text to wrap at a typical width.

But, if there are long code or raw text lines, or any embedded image or markdown table or other structure that is inherently wide, I want it to overflow and use that extra screen space, not get clipped into this ridiculously narrow bowling lane. That's my instinctual desire and the only reason I would expand the browser to full screen, and it is an utter disappointment to try that and be told, "no space for you."