I'm pretty sure the HN reader uses the Android webview [1] to render all webpages, which is the same thing that is used in the Android Browser. Chrome Mobile is not available for download on devices before Android 4.0, and didn't become the default browser on Android until 4.2.
According to these stats [2], Android Browser has about 55x the usage of Chrome Mobile as of April 2013. This means ~97% of Android devices will likely show up as they do in my screenshot.
In short, the problem is not with my HN reader, the problem is with this CSS library on the most common Android browser.
[1] http://developer.android.com/reference/android/webkit/WebVie...