Valves normally match much higher impedances than that of a loudspeaker.
The output of a given microphone delivers the same power whether it is low or high impedance.
Line inputs present a much higher impedance, typically 10 kΩ or more.
In three-state logic, an output device can also be high impedance.
The choke presents a high impedance to the ripple current.
It also gives it a higher impedance (lower current for the same voltage).
This is one of the few standard hand held devices which can drive high end & higher impedance headset's with considerable volume.
However, it has been noted that high impedance from one device will still interfere with the bus values of other devices.
Due to the high impedance of the ground, the current "chooses a better conductor", namely a person's legs, passing through the body.
No point is connected with earth (isolation), except perhaps via a high impedance.