That comment got away from me in length, so to summarize: I've been an add-on developer for Microsoft's competing product since the TAP (beta) program for OCS

That comment got away from me in length, so to summarize: I've been an add-on developer for Microsoft's competing product since the TAP (beta) program for OCS and part of a few organizations who used it as their only telephony/messaging product but people used that product differently. As part of a project between the two TAP programs, I wrote a dashboard site that provided stats about the operation of the on-prem installation, mostly centered around telephony, but included a lot of information about who was "tagging users for status change alerts" (without details, just rolled-up), IM-only conversations (this was tricky) and stats about interruption with regard to user's status. My personal experience was that we communicated more frequently via IM and had fewer "missed connections" on Teams, resulting in fewer escalations to less convenient forms of communication (and less of a feeling of being ignored). It is my belief that this happened because Teams provided rich information about the status of the user (and also didn't keep IMs around so you didn't expect them to follow-up later if they didn't reply in a few minutes). Unfortunately, I have no such insight into Slack's back-end, but anecdotally, I am interrupted far more through Slack than I was in Teams and my messages go unanswered far more often to the point that in Teams where I positively relied on status before sending a message, I don't even look at it in Slack because it doesn't help me to decide whether or not I'll be better off picking up the phone or e-mailing.