Using Firefox 22.0 on Ubuntu 12.04, English Wikipedia User:Hhhippo notes that "I see an empty line between ''User guide'' and ''Leave'' and another one between ''Leave'' and ''feedback''. My very first thought was that ''Leave'' would be the switch for signing out of the beta test (note that I didn't click it ;-)"
The culprit, evidently is "Ubuntu's default font: DejaVu Sans. That's a bit wider than e.g. Arial, so it causes a linebreak in the link. Maybe one could make that space non-breaking and have the flyout widen instead?"