> Once again, "I, as a tech-savvy person, can operate my highly-customized XMPP setup everywhere", while ignoring that most people do not run their own servers.

I said "my server", but the exact same code could be pointed at a different server by simply changing the username/password. Compare this to having to port a codebase from Signal to WhatsApp/Slack/whatever.

I'm also just using a standard ejabberd-based deployment, nothing highly-customized about it. Have you tried a Signal server deployment? I have, and THAT is the definition of highly-customized.

> This was discussed numerous times various platforms and proven wrong.

Alternative clients exist, but they are heavily frowned upon by the community - as a lot of the functionality they add (disappearing messages, view once media) depend on people using the official clients and not custom ones that could simply ignore this functionality.

> As discussed before on this page, most XMPP users don't run their own XMPP server but use a public XMPP server on the internet. Nobody can check whether this public XMPP server tracks its users without accessing the server itself.

That's fine, same thing applies to Matrix/Signal/WhatsApp/pretty much any messaging service out there.

> So, do you assume the Signal network infrastructure consists of a single server?

Functionally - although it is clustered - it is a single server, run by a single team - and it has gone down multiple times in the past few years.

And when it does go down: good luck using that Signal client to talk to anyone over it (SMS doesn't count as it has zero security on Signal and isn't even available on the iOS client). At least with XMPP, I can point the same client to some other server and potentially continue a conversation with someone somewhere else, with the exact same OMEMO/PGP encryption.

That is why decentralized/federated is better than "all your eggs in one basket" centralized. Centralization provides one with convenience, right up until it stops working and then it becomes a massive inconvenience.

> At least Quicksy (from the Conversations developer who bragged in a public video about copying WhatsApp/Signal) and Kontalk require a phone number.

The whole point of Quicksy is to allow people to try XMPP and find contacts easily with their number before they then move on to using actual JID-based accounts.

And he's more than free to brag about what he does - he's the one that spent the time; writing code and extensions and then released the thing to the public as free and open-source code.

> Signal does. You wrote, you use Signal. Did you ever join a Signal group? There is a dialog when entering a group the first time.

This is your Signal PROFILE name, not a username. You can quite clearly see this described in Settings -> tap the top bit with your number and read the text at the bottom.

People can still see your phone number by simply clicking on your user in the group member list. Signal, at the current time[0], has zero username functionality.

[0]: https://twitter.com/moxie/status/1480643863970816001