jack_plug is a pretty bad name for this tag, I've never heard that phrase in my life and when I saw this thread I assumed that it was about car parts. I would definitely prefer an alias to audio_jack.
post #1688923 is still an audio_jack, even if it is not currently being used to transmit audio, likewise with the Satori examples. The 1/4" jack itself (and the 1/8" jack, e.g. in post #1127722) has exactly one actual function, which is transmitting audio (including phone line audio), and it remains audio equipment when used for other purposes (the same way a microphone remains a microphone when its being used as a dildo).
Jirou Kyouka's earlobes are more of a problem because they seem to be flesh in the shape of an audio_jack, not an actual jack. But calling them jack_plugs doesn't really fix the problem, because that's also primarily supposed to be the connector itself, not "anything shaped like the connector". I think her earlobes can be called audio_jacks just as easily as they can be called jack_plugs, because they're very obviously supposed to be an imitation of these connectors (and canonically they do transmit audio).