Maybe it would need to draw on experiences of moderating chat rooms and forums - these are very often done by volunteers who put a lot of time and energy into it because they believe in it.

There is also the “Web Of Trust” concept, where, given that everyone can prove their identity, people can then vouch for each other.

needs to quickly get past two network effects: the global network effect […] and the local network effect

Sounds like a job for Fedi-date! If you could somehow hook a dating app into the fediverse, then maybe it could survive long enough to get sufficient users. If it also offers more general IRL meet-ups (like meetup.com but without the corpo rent-seeking), then it could perhaps begin to get popular that way too.

I think their focus is America. America’s racial problems are quite unique to America, because slaves were just part of normal life in the US up until slavery was abolished. It was part of the fabric of society in ways that it just wasn’t elsewhere. Even in the UK, where many black people can trace their family trees to slaves in the West Indies, there were never slaves actually held on the island of Great Britain.

Things like segregated school systems are still very much in living memory in the US. So there are unique issues in America that Americans must heal from before they can really consider such problems in the past.

traffic statistics (through creepy location tracking, even in the background unless opted out)

yes it’s definitely creepy when Google does it, but it provides invaluable data to other users - advance warnings of tailbacks whilst driving, and accurate ETA for public transport when using bus or train. Would be great if a privacy-respecting way to do this could be found for OSM & its ilk.