It's not a competing standard, it's a whole new approach to decentralize forum-based social media.

ActivityPub is not fully decentralized, it's a federated design, meaning it's a network of instances, and each instance is just a regular website with servers. Anyone can run an instance, but it's expensive, tiresome and you'll get banned for it; they are regular websites.

whereas Plebbit is fully decentralized, it's purely peer to peer, meaning it's a network of peers where every peer can potentially be a full node by simply using the desktop app (or in the future, a non custodial public rpc on mobile), and you don't have to run any site/domain for it, it's censorship resistant just like running a torrent with a BitTorrent client.

Also to be clear: like ActivityPub is a protocol with clients, such as Mastodon and Lemmy, Plebbit is a protocol with clients, such as Seedit and Plebchan.

Definitely I could see this being useful for discussing things that would traditionally be censored on other more centralized or semi-decentralized platforms (piracy, anti-authoritarian discussions in an oppressive country, etc).

IPFS by default isn't set up to work around censorship or anything of the sort. Protocol Labs (creator/maintainer of IPFS and Filecoin) have always honored copyright takedowns, etc. on their own infrastructure and have done a fair amount of work on content blocking within the default IPFS clients and such.

e.g. https://blog.ipfs.tech/2023-content-blocking-for-the-ipfs-stack

Because this way it has no central server, database, HTTP endpoint or DNS - it is pure peer to peer. Unlike federated instances, which are regular websites that can get deplatformed at any time, plebbit full nodes are customized IPFS Kubo nodes, and running one is as simple as downloading the Seedit client desktop app (available on github) and keeping it open. It runs the node automatically, and seeds content automatically as you browse it. It runs on a raspberry pi, so we expect to see a lot of plebbit users running their own full node.

Apparently https://plebbit.com/

plebbit.com is just a landing page made by a member of the community, to explain the project. To use plebbit, you can check out its clients, like Seedit.

The downside is big instances decide which content to show their users. If lemmy.world defederates some instance that's content I would never know existed.