You have to consider that Firefox's main target is Windows, not Linux. Actually, according to the mozilla documentation, they specifically write code that is portable, and even has guidelines on how to do it. That being said, the program is different, only in slight ways between a Windows version and a Unix version. You can press ctrl-w to close a window (current tab). Pressing the same key when only one window is open will exit the program.
Well, but i see one difference - the orientation of "Restore Session" buttons on Win/Linux is opposite.. i get crazy all the time, because i'm switching OSes quite often.. So i guess, shortcuts should be preserved, and they should be equal everywhere.. even if it doesn't comply with other programs.. well - you get to used to program you use most often, and it doesn't really matter what OS you use.. Regards, Atis