@cferdinandi Not quite: signal provides you a way to send encrypted messages moderated by a server (that knows who talks to whom and when, but not the content; though Signal devs try to limit what they can know).
Hyphanet is a fully decentralized network that also hides this metadata by hiding messages among small encrypted pieces it uses for general communication and uploads to computers of other participants of the network.
So outside observers cannot see whether you write at all.