This is a very weird effect. I didn't notice it at all before, but examining the text that Jeremy highlighted I now see it, very faintly, in Opera on Vista.
The really weird thing is that the black bits appear only when I first hover the cursor over a text link. If I leave the cursor there and then change the screen magnification, up or down, (CTRL-Plus or CTRL-Minus), the black edges disappear. But then, when I go back to the previous magnification level, the black edges are no longer there!???!
But then if I hover over a different text link, the black edge is there again, and disappears when magnification is changed.
Totally bizarre, but it does seem to have something to do with the way the italic is rendered when reversed. The cure? Take three aspirin and call me in the morning (when I will tell you just to ignore the problem).