The main goal of these sites is link aggregation. It wouldn't be overly difficult for a federated server with its own /c/Technology community to see other posts from other communities linking to the same thing and combining the discussions into a single view.
The tricky part there is moderation, but even that's manageable by allowing moderators to remove content from a federated view within their own instance, it'll just be difficult when a small instance is dwarfed by a larger one.
That's true if of any power plant though. It'll still be cheaper and safer (if it ever works).