4chan would have entire threads devoted to building worse hells. Yes. Seriously. They really would. And then they would instantiate those hells.

They really would at that. It seems you are concerned here about malicious actual trolls specifically. I suppose if the technology and knowledge was disseminated to that degree (before something actually foomed) then that would be the most important threat. My first thoughts had gone towards researchers with the capabilities and interest to research this kind of technology themselves who are merely callous and who are indifferent to the suffering of their simulated conscious 'guinea pigs' for the aforementioned <stupid reasons>.

So if you ever have an insight that constitutes incremental progress toward being able to run lots of small, stupid, suffering conscious agents on a home computer

At what level of formalization does this kind of 'incremental progress' start to count? I ask because your philosophical essays on reductionism, consciousness and zombies is something that seems to be incremental progress towards that end (but which I certainly wouldn't consider a mistake to publish or a net risk).