It gives control to the node operator. You join a node on the basis that you like the operator and trust them to federate responsibly. The end user is along for the ride with the node operator.
That's not how it works in the case of WordPress though, in this case it's not posting to some account on someone else's instance, each blog is it's own ActivityPub instance (as they just add support for the ActivityPub endpoints to the existing hosting)