weigh yourself every day, and don't eat for the rest of the day when you are above the center line

That has some issues. First, changes in water retention jitter your daily weight by a pound or two. Second, you assume good tolerance for intermittent fasting. If you weight yourself in the morning, decide you're not going to eat for the whole day, and then suffer a major sugar crash in the afternoon, that will be problematic.

weigh yourself every day, and don't eat for the rest of the day when you are above the center line.

Do scales actually work with enough accuracy that doing this even makes any sense?

Take the food example. Technology has enabled food to improve.

And has the presence of food based superstimuli, a.k.a., junk food, improved to worsened our diets?

If you eat less and exercise more then, indeed, you will lose weight.

Surprisingly, some people don't even believe this. I know a sizable group of Paleo proponents and some fruitarians who say that you can eat whatever quantity of food x and this will not have negative effects on your weight. There are also people who think this advice won't work because they've tried and it didn't had any effect (but actually they weren't aware that they were not eating less).

But there are plenty of people for whom that doesn't work so well, and this is true even among very smart people, very successful people, or almost any category of people not gerrymandered to force it to be false.

I am between those people (those who fail to follow the simple advice, not the very smart or very successful). But I recognize that my failure is in proceeding to eat less from the simple cognition of "I must eat less". That doesn't make "eat less" useless, it makes it incomplete. Indeed, when I found a system that allowed me to eat less using whatever low willpower that I have, I indeed started to lose weight.

Sorry, "two" possible environments, not three.

The point is that Hell can be made arbitrarily likely by our choice of computing language - even in more complex environments, like our own world, thus creating an agent that does nothing (or that follows any particular policy).

I don't think I understand. What is the third possible environment? And why exactly is the behavior stupid? It sounds like it might be actually true that it is too dangerous to test whether you are in Heaven or Hell in that situation.

Most people can't imagine what a world without ageing would be like, and they can't want what they can't imagine.

I have to agree with Lumifer -- most people can imagine (and want) a world without aging, because they would not bother to think about the demographic trends. I would compare this to asking someone to imagine a world in which no one was living below the average income level; I think most people would agree that this is easy to conceive of, and desirable. It's only the select few who would think this through and wonder how the powers that be are going to achieve this without doing something very drastic to a lot of people.

How do you express, Fermat's last theorem for instance, as a boolean combination of the language I gave, or as a boolean combination of programs? Boolean algebra is not strong enough to derive, or even express all of math.

edit: Let's start simple. How do you express 1 + 1 = 2 in the language I gave, or as a boolean combination of programs?

Basically the problem is that a Bayesian should not be able to change its probabilities without new evidence, and if you assign a probability other than 1 to a mathematical truth, you will run into problems when you deduce that it follows of necessity from other things that have a probability of 1.

Any program that reads this post and these articles wasn't stuck in a sandbox anyway.