As stated in the title, the Search while typing option breaks the youtube hotkey to open the full screen with the F key. I assume it will behave similarly on any website that takes full screen from a single key hotkey but did not yet have the time to find and test such sites. It took me some time to figure out that was happening when I was trying to open a video into fullscreen because it was not only causing the video to open the full screen and close it again directly after, but it also scrolled the page down. I don't know to what extend firefox can do anything about this issue but perhaps a note/warning next to the option telling users about this would be helpful for people like me who want to try out settings they don't fully understand and they get unexpected and hard to explain behaviour out of "nowhere".