Glad to hear about your successes in the trip! I’m still incredibly early in my own studies, but I’ve heard the best way to study listening comprehension is by regularly consuming media in the language. What that looks like might change depending on someone’s particular interests, but I’ve really enjoyed putting on Japanese Twitch streams in the background for games I already know (or don’t have any need to know, like competitive esports).
As expected, quite a lot flew over my head. But I was also surprised by how much I picked up on, both from the gradual improvement of my more formal studies and also from the loan words that tend to show up when talking about games. And I’m able to leverage my existing knowledge of the subject matter to just let my brain do what it can to contextualize what it’s hearing.
In no way is the person you’re responding to speaking defensively. They’ve discussed the reason why your extrapolation to a full-mesh connective worst-case scenario isn’t based in the reality of how ActivityPub functions. But you don’t seem to be willing to entertain the notion that the federation of any given action never exceeds the number of instances subscribed to the community that generated it.
Even should every instance subscribe to every community on every other instance, the recipient of a federated action doesn’t turn around and rebroadcast that action back on to the network because it is not the authoritative host of that community. Therefore what this discussion is lacking is proof of where this exponential broadcast storm of federated actions comes from in your assertion.