For some reason, they've gone to considerable trouble to avoid using CSS text-decoration to underline their links - which could be expected to work pretty well everywhere - and instead implemented custom "underlining" using an SVG background-image. I guess Safari on iOS doesn't position the background quite how they expected.

Designers: when you're tempted to do something like this, presumably because you think you know better than the browser precisely what an underline should look like... just don't.