[Steltek]

How would up/down votes work on a decentralized platform? Wouldn't it be easy to game by standing up your own server and wishing up a legion of sockpuppets?

There's a whole Moonshot of spam resistance that's going to need to happen in Mastodon/Matrix/Whatever.

[nine_k]

Decentralized networks need trust, and trust is not a Boolean value.

With a centralized service, trust is simple: how much you trust the single entity that represents the service.

In a distributed network, nodes need to build trust to each other. In the best-known federated network, email, domain reputation is a thing. Various blacklists and graylists pass around trust values in bulk.

So a node with a ton of sock puppets trying to spam votes (or content) is going to lose the trust of its peers fast, so the spam from it will end up marked as such. A well-run node will gain considerable trust with time.

This, of course, while helpful, does not guarantee "fairness" of any kind. If technology and people's values clash, the values prevail. You cannot alter values with technology alone (even weapon technology).

[dboreham]

The problem you describe is called Sybil resistance and is known to be hard, but there are some example working systems such as Bitcoin.