Comment 6 for bug 1497475

This is almost surely by design. It happens in both OSes and, in the system ("BIOS") settings, permanently reversing what the Fn key does also reverses it for everything except PrtScr and the WiFi kill switch. The consistency under all those conditions strongly indicates that it's on purpose.

The difference between muting and turning WiFi off is that most people have experience with various electronics having a mute feature (silencing your cell phone at a movie theater, for example). There's also a universal method of fixing the problem: either turn the volume up or unmute. Almost all people know to do one or the other.

People don't have much experience with WiFi kill switches. They don't usually know that they even exist. So when they accidentally flip the switch, it appears that WiFi is broken. Even the normal ways of fixing a broken WiFi connection—bringing up the list of nearby access points and selecting one—appears broken. They can't fix it in the normal way, and they don't know the correct way. That's much worse than accidental muting.

Then they waste the time of Dell's technical support line.