The context of email, in my experience, is that "you'll get the email when you see it." Slack's ephemera, the social contract that it encourages, is "you are on all the time." It is an asynchronous communication tool that it tries to convince its users is synchronous, and if you aren't using it in a synchronous manner (as I don't, for the most part), you are breaking that perceived illusion. You are not being a Team Player.

There is a significantly different social implication to clicking the "fuck your do-not-disturb settings" link and calling you. (I would argue that the former should be worse, but it isn't, ever.) Ephemera matters. Context matter. Slack creates a bad context. They own that.

Slack's job is to make communication easier, and apparently it is doing just that based on its massive user base spike. I'm signed into 6 different Slack org's right now on my laptop to let me talk to different clients all at once and is extremely easy to use and a great timesaver.

When I leave my desk my phone gets direct messages to me that I've missed. It is incredibly useful and is doing it's job. All of the complaints above are all just deflecting your company's lack of respect for your personal time. Don't feel like being on instant messenger away from your PC? Don't install it on your phone, or turn mobile notifications off.

I've worked at previous jobs where my manager would send emails at 1AM to my BlackBerry and expect a quick response. I didn't blame BlackBerry for that, I blamed my previous management for expecting me to be online 24x7.