“…the mutual understanding does not carry with it any obligation…”
Of course not. Mutual understanding allows the undertaking of obligation. I’d say it’s a prerequisite to a contract of any sort.
“By contrast, your "social contract" imposes obligations I can't get out of.”
You’ve been told several times you can opt out one way or another.
“I can't notify the IRS that I'm not paying their protection money anymore.”
Well, you could. But most people who opt out of the social contract aren’t quite that blunt.
“If a police officer bashes in my door, I can't shoot him in self defense. “
Actually you can, but if you do it should really be self defense.
“Your little flourish on the end is kinda cute.”
It wasn’t meant to be cute. Take it at face value. Why would I address the matter if it did not please me to do so for some reason? Right now, it does not please me to address why some things are pleasing, others are not and what that all means. (For the casual lurker what I wrote was: I see most of your PS (That’s not a typo, it was a post script.) as containing arguments in favor of the concept of the social contract, but it does not please me to address that right now.)
“…I can always refuse to enter into an implied contract by so stipulating. A "social contract" imposes terms on me that I can't escape by any means, even though I didn't agree to it.”
To over simplify, in the end the basic terms of either contract are the same: You don’t get what you would get if you had entered the contract.
“Cultural norms tell Americans that they should assume they can ring my doorbell; in Gondwanaland, cultural norms tell people that they should stand back six camel-lengths and whistle Dixie instead.”
And
“Deep in the backwoods of Yakutsk the situation is exactly reversed:”
I’d say the two places have different Social Contracts, but I realize you wouldn’t.
Yes, exactly. That's why cultural assumptions aren't "contractual" in nature.
You’ve been told several times you can opt out one way or another.
The only way I can opt out is by submitting to a violation of my property rights. I own land. It's mine. If I want to "opt out" of this contract I never opted into in the first place, then I must allow my land to be stolen from me.