The author nails my thoughts on Slack (and its OS clone Mattermost). It is less a communications tool, more of a productivity tracker.

I've worked in places where it was unofficially compulsory to have Slack always open. If you didn't respond to a message is a timely fashion then you'd be asked why. It became the case that Activity on Slack = Productivity.

This wouldn't be so bad if it weren't for the fact that I think Slack is a pretty poor way to do workplace communication. It's the textual equivalent of shouting out a question to the whole office. Everything seems to mush together in to one big conversation about everything that is hard to track and search.