[cperciva]

Negotiating voltage after being connected avoids the problem of sparking while the connector is being plugged in, but I don't think it helps with avoiding sparking in the process of unplugging the connector? Unless one of the leads is shorter so that is disconnects first and the circuitry can detect that and turn off the power super fast?

[crote]

You are absolutely correct, and the USB-C specification even has an entire appendix dedicated to the problem. The trick is to reduce the voltage difference until the plug is far enough that a spark is no longer an issue, which means placing an appropriately large capacitor at the Sink side.