I do think toxicity is often extremely subjective. Ironically the limits and definitions are often defined by the most toxic people, because they have the least tolerance in general. But that is just my opinion.

I don't know what limits HN uses. You are green at first when it is euphemistically true. You aren't allowed to downvote at first (although restrictions always apply to direct responses?). Generally I would describe the limits as minimally invasive. I would guess the average upvote score for a comment on HN is probably something about 3?

These mechanisms are quite smart and not too invasive, but not the sole reason for HN being like this.

For your network it highly depends on what audience you want to nurture. Do you want the classic golf club where people feel superior and exclusive to others? Use vouching and ID checking.

Do you want free thinkers? Don't moderate much, but you may have to gatekeep people looking for offence (or just don't feed the trolls and ignore them).

Do you want a broad audience or enthusiasts? "Exploitability" is not only a matter of education, but it certainly helps. If that is a problem on your platform, you need to find out about the type of exploitation to counter it.

Not everyone is alike and will get along, there are different personalities having different expectations. If you cater to all, you probably won't be successful.

I cannot say what attracts people preferring "pleasant" (meaning?) discussions on the net. I probably more or less belong at the other end of that spectrum.