I have extended the iris.to Nostr client, into a clone of the site with a  reputation system on it (prof of concept). It works, but it is still fairly simple: https://dpeep.com. 
You can trust people and posts, and the trust network extends 3 degrees deep. You need to create multiple accounts and trust each other to see the effects and the networks of web of trust.
I'll write some posts about how the general system works later.