Here's another way of looking at the situation that may or may not be helpful. Suppose I ask you, right here and now, what you'd do in the hypothetical future Parfit's Hitchhiker scenario if your opponent was a regular human with Internet access. You have several options:

1. Answer truthfully that you'd pay $100, thus proving that you don't subscribe to CDT or EDT. (This is the alternative I would choose.)

2. Answer that you'd refuse to pay. Now you've created evidence on the Internet, and if/when you face the scenario in real life, the driver will Google your name, check the comments on LW and leave you in the desert to die. (Assume the least convenient possible world where you can't change or delete your answer once it's posted.)

3. Answer that you'd pay up, but secretly plan to refuse. This means you'd be lying to us here in the comments - surely not a very nice thing to do. But if you subscribe to CDT with respect to utterances as well as actions, this is the alternative you're forced to choose. (Which may or may not make you uneasy about CDT.)