I'm not sure when exactly, let's say a month ago, but something changed in the Firefox behavior when reopening closed tabs. When I pres Ctrl-Shift-T to restore the last closed tab of the current window, Firefox restores in the current window the last closed tab in any window. Example: you have 2 Firefox windows open and close first the tab X in window 1 and then the tab Y in window 2. If you go back to window 1 and press Ctrl-Shift-T, Firefox will reopen the tab Y (the last closed) in window 1. I don't know when this changed, but before this modification Firefox restored the last closed tab in the current window, i.e., it restored tab X if you were in window 1, and tab Y if you were in window 2, but it never restored tab X in window 1.
This may seem like just a minor detail, but it was a very useful feature for people like me who work with multiple windows.
