For better or worse, HN is a non-siloed site (
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...), meaning everyone sees the same things and is in one big room together. There are certainly design choices there, but each online community has its initial condition set and its pros and cons that flow from that. I don't think it's a question of perfection. It probably would not be wise to mess with those initial conditions—that would likely cause unintended consequences, so the bar to clear to justify it would have to be very high.
I've written about the pros and cons of the non-siloed format here, if anyone's interested: https://news.ycombinator.com/item?id=23308098. It leads to a rather paradoxical situation.