See. Before 'Slack', we had 3 channels of communication. 1. Email (usually expectation of getting a reply within hours) 2. Phonecall (reserved for urgent situations, expecting a reply within... seconds) 3. Ticket system that had a little drop-down where you could select urgency. And you would expect a reply based on the urgency.
If you abused the urgency, we had a way to track that, and let you know.
Today however, Slack's "multiple organizations" feature pretty much shadowed the above. Now product manager from client org X, will require that you make a channel called "X-feature Commandos/dream team" then invite everyone involved on the project. Then they will ALWAYS end up wasting everyone's time for no reason. "Hey @here, X page is slow can you check it out?". "Sorry guys my bad. I was under the bay sea riding the Bart! Forgot LTE connections can be finnicky 100m under water. heh (ultra fast parrot emoji)"