There's a lot by way of answer to this in a 2009 essay by Paul Graham, "What I've Learned from Hacker News", written after the site had been live for about two years: <http://www.paulgraham.com/hackernews.html>

It's been discussed several times on Hacker News itself, of course, notably at the time (<https://news.ycombinator.com/item?id=495053>) as well as in 2012 (<https://news.ycombinator.com/item?id=4285333>) and 2019 (<https://news.ycombinator.com/item?id=19210923>).

This addresses general issues around moderation, including things that seem to be especially harmful: dilution, the distinction between behaviour and people ("It's bad behavior you want to keep out more than bad people"), "broken windows", the "two major types of problems a site like Hacker News needs to avoid: bad stories and bad comments", the Fluff Principle ("on a user-voted news site, the links that are easiest to judge will take over unless you take specific measures to prevent it"), and the "two main kinds of badness in comments: meanness and stupidity".

Graham doesn't get into why one set of moderators is essential, but I'll suggest this: editorial voice.

When you visit a traditionally-edited news source --- news paper, television network, magazine, radio network --- what you'll find for most of these is a specific editorial voice. The Financial Times, Fox News, the New York Times, Breitbart, The Daily Caller, The PBS News Hour, the Daily Mail, the Guardian, the BBC, NPR's All Things Considered ... each have a distinctive voice. Like it, love it, despise it, or hate it, it's there.

For a discussion site, a problem with offering moderation-as-a-service is that the moderation you see is not that which others will see, and for at least some members, that means seeing a lot of what would be considered "dumb comments". On which Graham said:

Bad comments are like kudzu: they take over rapidly. Comments have much more effect on new comments than submissions have on new submissions. If someone submits a lame article, the other submissions don't all become lame. But if someone posts a stupid comment on a thread, that sets the tone for the region around it.

That is, the problem is that multiple moderation views means that those bad comments --- mean, stupid, or both --- are going to dominate the conversation. As it stands, HN tends to weed these out reasonably quickly (flags and downvotes really help, don't feed the trolls, and email the mods at hn@ycombinator.com in egregious cases).

In practice, different moderation philosophies are best enacted through multiple channels. For sites such as Reddit, this means different subreddits with different moderation policies. For Hacker News ... you'll have to go to a different discussion site, maybe lobste.rs, Tildes, Lemmy, or kbin, say. Keep in mind that even on Reddit there's often considerable "bleed-over" between different subreddits (a chief annoyance of mine there, and a reason I'd largely abandoned the site well before the current contretemps).

I've seen subreddits which have relaxed rules, or permitted certain types of content on specific occasions ("low-effort Fridays" being one variant), and ... it still strikes me as highly corrosive.

On Tildes, a text-only site, a newly-arrived Reddit refugee suggested enabling images on the site. That's ... not been well received: <https://tildes.net/~tildes/16fe/considering_image_posts_on_t...> (I've posted my own brief objection, though there are many well-considered ones by others.) This comment by a former mod of /r/photography explains how and why images can absolutely change the entire dynamic of a subreddit even one devoted to the topic of photography: <https://tildes.net/~tildes/16fe/considering_image_posts_on_t...>

Graham did open his essay with the observation that both the format of HN, and HN itself were, at the time, young. I'd argue that neither are, with Hacker News now in its 17th year. However Hacker News still remains in large part true to its founding vision. It is also still a useful and valuable online forum. Not perfect by any means. But far better than much else that's come (and often gone) in the meantime, and in particular durable in ways that few other fora have been.

Play with its formula with extreme caution.