Unlike in real life where someone can come and distract your full attention, IM gives you the ability to set your status to 'Busy'. Seems far better at dealing with interruptions to me.
https://get.slack.help/hc/en-us/articles/214908388-Do-Not-Di...
If someone sends you a direct message they have the option to interrupt you if it's really important.
That's a minor thing but 'Zzz' really sends the wrong signal to the sender: if you are not available, then you are sleeping (i.e. unproductive).
Other chat systems offer the ability to attach a message to your AFK status, which can be pretty helpful for setting expectations about when you might be back. Last time I looked, Slack seemed kind-of resistant to doing anything like that.
Working remotely, is that a bad thing? If you are unavailable due to deep coding or a need for a nap does it matter?