What if you limit accounts to real people and then keep track of their credibility? It's some initial effort but how could the ranking be manipulated when all dishonest people have burned their credibility?
I'm sure you could still manage to make "fake" accounts but it would be much more difficult, and linking them together would be much easier.
Of course starting a site like this would be very difficult. But maybe you could start without it then add it in once you get to a decent popularity such that many people can find a referral if they need to.
In China, all social accounts must be associated with a phone number, and phone numbers are tied to government identities. It doesn't stop any manipulation of scores and rankings.
> then keep track of their credibility?
It is very likely China will do that too soon. I think you can already imagine the ramifications.
However it could just be reputation based like on Wikipedia