This was a great post, really appreciate the summary and analysis! And yeah, no one should have high certainty about nutritional questions this complicated.

For myself, I mostly eliminated these oils from my diet about 4 years ago, along with reducing industrially-processed food in general. Not 100%, I'm not a purist, but other than some occasional sunflower oil none of these are in foods I keep at home, and I only eat anywhere else 0-2 times per week.  I did lose a little weight in the beginning, maybe 10 lbs, but then stabilized. But what I have mostly noticed is that when I eat lots of fried food, depending on the oil used (which to some degree you can taste), I'm either fine, or feel exhausted/congested/thirsty for basically a full day. I think you may have a point about trans fata from reusing oil, since anecdotally this seems even worse for leftovers.

Of course, another thing I did at the same time is switch to grass-fed butter  and pasture-raised eggs. Organic meats and milk, not always pasture raised. Conventional cheeses. I've read things claiming the fatty acid composition is significantly different for these foods depending on what the animals eat, in terms of omega 3/6 ratios, saturated/unsaturated fat ratios, and fatty acid chain lengths. I've never looked too deeply into checking those claims, because for me the fact that they taste better is reason enough. As far as I can tell, it wasn't until WWII or later that we really started feeding cows corn and raising chickens in dense indoor cages with feed? Yet another variable/potential confounder for studies.

In what sense are these two viewpoints in tension?

This seems more a question of "observable by whom" vs "observable in principle."

This works too, yeah.

Yeah, I was thinking it's hard to beat dried salted meat, hard cheese, and oil or butter. 

You also don't have to assume that all the food travels the whole way. If (hypothetically) you want to send 1 soldier's worth of food and water 7 days away, and each person can only carry 3 days worth at a time, then you can try to have 3 days worth deposited 6 days out, and then have a porter make a 2 day round trip carrying 1 day's worth to leave for that soldier to pickup up on day 7. Then someone needs to have carried that 3 days worth to 6 days out, which you can do by having more porters make 1 day round trips from 5 days out, etc. Basically it you need exponentially more people and supplies the farther out your supply chains stretch. I think I first read about this in the context of the Incas, because potatoes are less calorie dense per pound than dried grains so it's an even bigger problem? Being able to get water along the way, and ideally to pillage the enemy's supplies, are also a very big deal.

I think at that point the limiting factors become the logistics of food, waste, water, and waste heat. In Age of Em Robin Hanson spends time talking about fractal plumbing systems and the like, for this kind of reason.

All good points, many I agree with. If nothing else, I think that humanity should pre-commit to following this strategy whenever we find ourselves in the strong position. It's the right choice ethically, and may also be protective against some potentially hostile outside forces.

However, I don't think the acausal trade case is strong enough that I would expect all sufficiently powerful civilizations to have adopted it. If I imagine two powerful civilizations with roughly identical starting points, one of which expanded while being willing to pay costs to accommodate weaker allies while the other did not and instead seized whatever they could, then it is not clear to me who wins when they meet. If I imagine a process by which a civilization becomes strong enough to travel the stars and destroy humanity, it's not clear to me that this requires it to have the kinds of minds that will deeply accept this reasoning. 

It might even be that the Fermi paradox makes the case stronger - if sapient life is rare, then the costs paid by the strong to cooperate are low, and it's easier to hold to such a strategy/ideal.

This seems to completely ignore transaction costs for forming and maintaining an alliance? Differences in the costs to create and sustain different types of alliance-members? Differences in the potential to replace some types of alliance-members with other or new types? There can be entities for whom forming an alliance that contains humanity will cause them to incur greater costs than humanity's membership can ever repay.

Also, I agree that in a wide range of contexts this strategy is great for the weak and for the only-locally-strong. But if any entity knows it is strong in a universal or cosmic sense, this would no longer apply to it. Plus everyone less strong would also know this, and anyone who truly believed they were this strong would act as though this no longer applied to them either. I feel like there's a problem here akin to the unexpected hanging paradox that I'm not sure how to resolve except by denying the validity of the argument.

On screen space:

When, if ever, should I expect actually-useful smart glasses or other tech to give me access to arbitrarily-large high-res virtual displays without needing to take up a lot of physical space, or prevent me from sitting somewhere other than a single, fixed desk?

On both the Three Body Problem and economic history: It really is remarkably difficult to get people to see that 1) Humans are horrible, and used to be more horrible, 2) Everything is broken, and used to be much more broken, and 3) Actual humans doing actual physical things have made everything much better on net, and in the long run "on net" is usually what matters.

On the Paul Ehrlich organization: Even if someone agrees with these ideas, do they not worry what this makes kids feel about themselves? Like, I can just see it: "But I'm the youngest of 3! My parents are horrible and I'm the worst of all!"

And this, like shame-based cultural norm enforcement, disproportionately punishes those who care enough to want to be pro-social and conscientious, with extra suffering.