I wrote a follow up to both your article and the original one. https://medium.com/@rnotani/the-different-frustrations-of-sl...

Here is a relevant quote from the article.

"In my opinion both of these posts get it partly right. Both of these articles also have as a subtext an implicit or explicit comparison with email. Both, Slack and email tend towards “communication overload”. However, the generic description of “communication overload” obscures the very different type of overload created by these two technologies. Understanding this distinction also leads us to a possible solution.