Earlier quoted context omitted.
> Slack is fine and works fine. As a user, you can very easily turn it off and on at will, mute it, even set status messages like "I will check my messages twice a day". From a workflow standpoint, this is optimal. The catch is that many people view Slack as e-mail but with an expectation of instant response. The farther your Slack communications stray from engineers, the more likely you are to encounter this mindset…
>> The catch is that many people view Slack as e-mail but with an expectation of instant response. I don't get this, because email is instant response. It arrives more or less instantly. Almost all digital non-verbal communications can invite an instant response. Why is Slack so different than email? The excuses are the same... "Well, I didn't have Slack open..." "Well, I didn't have Outlook open..." Hell, you could…
On Slack, like any other instant messaging (especially the ones where the fact that you've seen a message is communicated to the other side), you don't have this option. You can, of course, snooze messages, but I doubt many people even know about that option, and a high fraction of those who do know just find it, at that moment, easier to answer immediately then to think about "scheduling" that answer.
Combining this with other characteristics that make online chat more like in-person chat (from simple functions like the ease of sending messages by pressing Enter, to more advanced ones like seeing when the other side is typing), it shifts the behavior, and people feel compelled to respond instantly - both by the expectations set by others ("everyone responds instantly to Slack so I have to as well") but maybe even more importantly by subconscious "burden" of not responding to an "already opened message".