The way to preserve what HN has that is good (and I'm not saying it's great, only that it's better than it might be) is to have a clear set of principles and communicate them. If you know a better set of principles, where the fitness function is high-quality discussion at scale, I'd love to hear what they are. Otherwise I'm going to suspect you of magical thinking, in which HN's current level is assumed to just happen for free, and for some reason meddlesome thought police keep intruding on it.
I guess I would draw a clear distinction between aggression and sarcasm. I do believe you that it's a difficult task to make things function healthily at scale and I'm sure those involved in issuing recent guidelines were correct to do so. And of course I agree that we shouldn't be aggressive (though waveform apparently needs a reminder of this). But I'm pretty uncomfortable with eliminating sarcasm. That's really a very common mode of communication in some cultures. It feels very sterile/corporate to not be allowed to simply be sarcastic. Especially when the target of sarcasm is basically western hegemony, as it was here!
The guidelines don't rule out sarcasm. They ask for comments to be civil and substantive. The Venn diagram of those things may not have a lot of common area but there's definitely some. Just don't ask me to specify what it is—that's probably too hard.