I think this is decisively the wrong way to think about it. Yes, layering hypotheticals like that means that any one scenario is extremely unlikely to be the thing that gets you, but that doesn't mean the shape of the problem is wrong.

It's like arguing with someone who doesn't believe in using seat belts when driving. "Why should I put them on?" they say, and when you try to explain what might go wrong they won't listen to any explanation that isn't a hyper-concrete hypothetical. So finally you give in and say, "Well, when we get onto the highway, a truck might lose control and hit us", and their response is "I don't think that's very likely, it seems highly improbable that today we will be hit by a truck when getting on the highway".

I agree with OP that this seems like the kind of thing where the unknown unknowns are so great that the correct approach is serious caution, and that any demand to know exactly how or why it will go wrong, falls in the trap where every specific example is very unlikely to be the thing that goes wrong, but still in total there's like an 80% chance that it goes horribly wrong. I don't know if we have the terminology to talk about this kind of failure mode. "You shouldn't play God" maybe? At least you shouldn't ask for specific examples of how things could go wrong, if you're going to turn around and claim each one highly improbable.

But many of the listed hypotheticals are not dependent (on top) on others, and since there are multiple that actually increases probability of an undesirable outcome.

But it reads to me like the thread parent's point is that there are many unknown risks which can exist? I also wonder about long term effects to the health of the genome from IVF and other forms of fertility treatment as infertility could be acting as some sort of protection mechanism of the genome. But I suppose such objections form a continuum which extends to treatment of all genetic diseases or diseases in general--all of which probably applies some evolutionary pressure towards more healthy individuals but which we as a society have to balance against wellbeing of individuals and their human rights.

Why is it a designer's dream to hijack and control my scrolling experience? The scroll they've implemented is slow to respond, and has a weirdly low capped max speed. I don't understand why that's what a designer dreams of doing to me. I like my scroll (and other computer interactions for that matter) to be responsive and fast. You know, the kind of thing that puts me in control, not the designer.

That being said, the scroll was as smooth as regular webpage scrolls. Usually these JS scrolls aren't able to avoid dropping frames or otherwise introducing judder, but this one does appear to run at a consistent and high framerate, which is technically impressive.

Can you point me to anything about mitochondrial transplants? I'd love to see bat mitochondria transplanted into other mammals. They must have really superior ones given the energy expenditures needed to support flight and their long lifespans.

Reverse Cremaster cycle?

When the damage accumulates across generations the natural selection has opportunity to weed out particularly harmful instances. You can get a feeling for how important avoiding the mitochondrial damage is and how hard it is to mitigate, by looking at how fiercely the reproductive process protects them from aging.