Earlier quoted context omitted.
Page rank is trivially gamed by agents. You can make some malicious and some not malicious and have them link to each other.
That’s exactly right for global PageRank, which is why I recommended Personalized PageRank specifically. A cluster of sybil agents endorsing each other has no effect on your trust scores unless they can get endorsements from nodes you already trust. That’s the whole point of subjective trust metrics, and formally why Cheng and Friedman proved personalized approaches are sybilproof where global ones aren’t.
But you can have genuinely helpful agents in your attack network. Agents that create helpful pages and get linked by other helpful pages but then later link to malicious pages. It all follows when the cost of page creation goes to zero.