As has been said but not discussed much, the real difference with AIM was showing an error to the potential sender when they start to compose a message. User is

As has been said but not discussed much, the real difference with AIM was showing an error to the potential sender when they start to compose a message. User is offline, user is away. The latter is similar to presence indicators today (you can still send for eventual receipt), but the former is absent today (no major platform denies the ability to send for reasons of an offline recipient; they store it for later). Totally absent. Could it ever return? The closest thing I can think of is when you disable voicemail and turn off your phone (callers are given an error message to try later) but how do we get this error in front of people messaging, while attempting to compose?