To be fair, at least in iOS, the edge swipe wasn't implemented until iOS 7. Imgur has the same problem, annoying as hell, but that might be a reason to why they haven't fixed it. (Even though iOS 7 is soon a year old)
I'm running iOS 6 and it is insanely infuriating here as well: I keep ending up moving between articles while trying to look at the graphs, as I end up scrolling left/right "too far" expecting it to rubberband. (Note that when using iOS 7 I have no trouble navigating Safari with the new native gestures.)