TL;DR: Offline messaging is incompatible with non-intrusive synchronous communication. I think the main problem with modern IM software resides in letting the

TL;DR: Offline messaging is incompatible with non-intrusive synchronous communication. I think the main problem with modern IM software resides in letting the user send messages to offline recipients (offline as in "not actively using the application"). For modern IM to be "instant" or "synchronous", every user has to be able of being interrupted at any time by a message sent to them, by means of intrusive notifications; this means that "being offline" is no longer an option in modern synchronous communication, so major IM software designers did away with it altogether--e. g. WhatsApp. This didn't happen with MSN Messenger pre-2005, for instance. Sending a message was only possible if both parties were connected at the same time; the moment the recipient disconnected, the text box got greyed out and the chat effectively ended. This meant that every user had to deliberately decide to be available for other people to message them; it also meant that IM was truly "instant" at all times--except when people left for a few minutes, which prompted an "away" status on their part; nonetheless, the decision to be connected had to be consciously taken at some point. A solution could be designing IM software that respects your time and attention. This could be achieved by forcing users to actively use the app in order to receive messages. P2P IM apps like Briar[0] are like that by definition--it's a "technical-limitation-turned-feature" for me. [0]: https://briarproject.org https://briarproject.org.