But why do you think that? Energy use is a matter of availability, not purely of technological advancement. For sure, technological advancement can unlock better ways to produce it, but if people in the 50s somehow had an infinite source of free energy at their disposal, we would have boiled off the oceans before we got the Internet.

So the question is, at which point would the aggregate production of enough energy to cause climate change through waste heat be economically feasible? I see no reason to think this would come after becoming "immortal post-humans." The current climate change crisis is just one example of a scale-induced threat that is happening prior to post-humanity. What makes it so special or unique? I suspect there's many others down the line, it's just very difficult to understand the ramifications of scaling technology before they unfold.

And that's the crux of the issue isn't it? It's extremely difficult to predict what will happen once you deploy a technology at scale. There are countless examples of unintended consequences. If we keep going forward at maximal speed every time we make something new, we'll keep running headfirst into these unintended consequences. That's basically a gambling addiction. Mostly it's going to be fine, but...