One thing I'd do is find a way to minimize the detail line below the headline. It doesn't need to be as large - it tends to wrap into a second line (at least on my iOS 9.1 iPhone 5s).
The detail line also doesn't need to be as verbose, IMO...
e.g.:
200 points by foobar 8 hours ago | flag | 192 comments
Although I would recommend keeping the "192 comments" link at least as large as it currently is. That's probably the 2nd-most tapped-on link (after the link to the source itself), and it's fairly difficult to aim correctly on mobile. Making it even smaller will make it harder to tap.
I always go to comments before clicking on the article link. While I'm reading, post can go away from current HN page and it is hard to locate it again.
Ps. iPhone4 is not compatible with new layout at all.
One thing I'd do is find a way to minimize the detail line below the headline. It doesn't need to be as large - it tends to wrap into a second line (at least on my iOS 9.1 iPhone 5s).
The detail line also doesn't need to be as verbose, IMO...
e.g.:
could be simplified to