The analysis is accurate, but I don't agree with the framing.

First, trust is a bad term, because it's contextual and therefore ambiguous. A follow represent "I am giving you attention", which means you are not a spammer for me. (e.g. a bunch of bitcoiners follow Vitalik on X just to dunk on him).

Secondly, reputation is and should always be relative to a pov. If it's global, it's a cousin of the CCP social credit score.

So everyone has their view of who's reputable/not-a-spammer, and this view is influenced or enhanced by only those that are relatively close to you, e.g. your follows and their follows.

How? Personalized Pagerank is a great starting point.

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