This man has shown himself to be quite ignorant in his comments, here once again.

SimpleX does not depend on a central entity nor does it use a central coordination service, if you don't have your own Simplex server it uses Simplex servers nothing else. It's architecture is very similar to email, you can have your own mail server or use another person's or provider's mail server.

In Simplex the servers are only used to receive messages and are implicit in the contact's address. Each user has their own receiving server, it's as simple as that.