Continuing the discussion from Design suggestion box:
When I middle click on any link on any other site, a new tab is immediately opened, because that's how I've configured firefox. Here I just get "firefox prevented this site from opening up a pop-up window".
I don't want any new windows to be created without me specifically and intentionally creating them! They mess up the mental and visual categorization I use to optimize my workflow. On any other site I just middle-click when I want a new tab, left-click when I want to follow the link in the current tab, and right-click/select-new-window-from-choices if I want to open a new window.
Not sure what is going on to cause this, I suppose I better go look at the HTML... nope, the "Design Suggestion Box" link immediately above displays the behavior, but it's just a garden variety a/href type link. Maybe it's in the CSS?
EDIT: Jeff Atwood has a workaround here - pointing out that since discourse/bb don't plan on using any real popups, telling firefox to allow popups for this site should provide the expected middle-click behavior.