Earlier quoted context omitted.
The one counter-example I can think of for that is https://forums.rpg.net - it's quite a large community, and has been around for something like 20 years. The moderators are very active in the forums themselves, and they've learned from their experiences over time. It's not perfect, but as the community is still large and thriving, even in the Reddit/Facebook/Twitter era, I'd say they're doing a good job.
I mean, there are of course good moderators (I've surely seen some), but unless they already happen to exist in the community it is extremely hard to put good moderators to the existing community. It is even harder to discover good moderators anyway.
We've scaled up civilization by replacing the need for organic care with money. The need for money provides the "affects them directly" part[0], and job requirements provide the "value system" part. Unfortunately, having people do the work for money, instead of for the output of their work, introduces all kinds of well-known problems that plague us.
All this means that, to provide good moderation for a community, you have to either:
- Find moderators within the community, who already care about its health, or
- find people within the community who care about it and have money, to draft moderation standards, hire paid moderators to enforce those standards, and then police the moderators so that they're actually doing their jobs properly.
I think very large communities can work only if they're applying either method #2, or become subdivided into small enough sub-communities that method #1 can be applied.
(There's also a third method: start a religion. It's the other tried and true method of maintaining a system of values in a society. But it's tricky to pull off, and stops working when the group grows too large.)
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[0] - Which is why some people are worried that basic income could collapse civilization. As it is, most value in society is provided by jobs into which people are coerced by their precarious economic situation.