Author here! A few thoughts on this:

- First and (maybe most importantly), WebRTC in browsers requires a central server for signaling. So unless web browsers loosen that constraint, a "true" P2P web app without a central server is unfortunately infeasible.

- My understanding is that with Operational Transforms, the server is "special" — it's responsible for re-ordering the clients' operations to prevent conflicts. I mention a little later in the article that Y-Sweet is just running plain Yjs under the hood. So it is a central server, but it's easily replaceable with any other instance of Y-Sweet; you could fork the code and run your own and it would work just as well.

- Peers will only sync their changes if they're online at the same time. That means that the longer peers go without being online simultaneously, the more their local documents will diverge. From a user experience point of view, that means people will tend to do a lot of work in a silo and then receive a big batch of others' changes all at once — not ideal! Having a "cloud peer" that's always online mitigates that (this is true for any algorithm).