Interesting. So it's not quite as universal as I thought, thank you.

However, I've just gone into Totem, changed the settings to something
weird and, yes, on my PC gxine and VLC were both affected, so there's
clearly some sort of link - at least, on my laptop.

The more I lean about computers, the more convinced I am that they have
developed self-awareness - *nothing* can be so creatively malicious
without *some* conscious effort ;-)