I have expensive Sony headphones, where if you want to use MIC, you have to unplug it from the PC headphone socket and plug it into a USB adaptor.
However, if you logout with Double Press CAPS switched ON, and login next time with the headphones plugged into the headphones socket instead of the USB adaptor, the 'Talk Icon' is shown onscreen and you can't get rid of it, unless you unplug your headphone socket, and plug it into the USB adaptor, and switch it OFF (Double Press CAPS) !

Why don't I just play in USB adaptor mode all the time ? Because it is only 16bit sound compared to 24bit sound through the headphone socket.