How bizarre! It seems to happen exclusively when I middle-mouse-click the links, including the ones in this thread! And it only works the first time I click on it – after that, middle-clicking does nothing until I refresh the page. (I get a “Firefox prevented this site from opening a pop-up window” warning that I have to bypass before the window opens.) Control-clicking, shift-clicking, and control-shift-clicking produce nothing unexpected. I never knew something like this was possible.
(To be quite clear, middle-clicking links opens a page in a new tab everywhere else I’ve seen.)
