Messaging over the Internet (and why I like XMPP)

Given the current state of messaging/chatting over the Internet, the popular options are WhatsApp, Facebook Messenger, Telegram and so on. All these are owned by corporations and pretty much black boxes. Apps like Signal and Keybase are also available that primarily advertise privacy and encryption. They are also partially open-source. However, they lack one important aspect that I will come to shortly. Since all these are pretty-much well-known alternatives, let me cover a couple of others briefly.