Are you sure Youtube's keyboard shortcut for pause is "Space" for you? For me it's K, with J being jump backward a few seconds and L being jump forward a few seconds. I don't know if the media buttons (Pause, Rewind, Fast Forward) would also work as this keyboard pre-dates Windows 95 so it doesn't have anything like that. [ Yes I should buy a new keyboard... ]
Thank you, I hadn't realized there were separate keyboard shortcuts, even though the one for pause is indicated on hover.
Even though space conflicts with toggling the currently selected item (tab/space), it is the more common shortcut in video player applications, and is quite easy to reach. I also think that mouse clicking an element shouldn't change the keyboard selection to that one.
Not sure how those media control are interpreted, I think I usually set them to control the MPRIS interface, so they would at the very least work on KDE with plasma browser integration.
