I know that this test was concentrated on screen readers, and that it may be perfectly fine to hide links offscreen for screen reader users, but it causes serious issues for those who *can* see the links.
If links are moved out of the viewport, the focus indicator follows the links and disappears from view. If several links are hidden from view in this way, it could be (and actually is, which I found out from bitter experience) seriously disorientating for any screen magnifier, voice recognition or keyboard only users.
I’ve been advising some of our Ajax people who rely on context menus to hide similar functionalities off-screen (the infamous absolute-positioning-to-the-left) to make them accessible to screen readers. Well, it’s time to revise my position, it seems. Or sophisticate it a bit and add another layer of behaviour that would put them back on-screen when focused.