Why I Won’t Ever Again Use Slack
I’ve had this unpleasant opportunity to use Slack. It seemed OK, till I tried to do something reasonable with it. In this little text I want to explain my particular hatred for Slack.
Worth reading — it’s “Why Slack is inappropriate for open source communications” but I’d rather call it “Why Slack is inappropriate.”
Who can view Your communications?
That would be it.
Slack is not end-to-end encrypted. Slack employees can read it, l33t crackers can read it, everybody can read it.
Well, actually, everybody apart from You. See the next paragraph.
Is it free?
No. Neither like in beer or in speech.
Well, there is a free plan but it has limits. For example, You can only see 10k last messages. Imagine Your teem has been writing about the new product and something important is mentioned but You go on. Later You want to go back to it but—Oh no!—it’s past the limit. You’ll never get it back. Such a shame. Can’t anything be done? No! Why? Because they can, that’s why, because You have been used.
Is it standardised
Although it tries to deceive You into thinking it is one. It tries to deceive people into believing they can use their favourite client—it pretends that it can be used with via XMPP or IRC. The truth is it doesn’t work. Believe me—or check on Your own—You can only see the messages that were sent when You were online. Moreover, not all of them.
(Update: May 2018) Slack doesn’t provide IRC/XMPP bridges any more.  The official statement is no longer available.
Seems like they took somebody without time, knowledge, or resources to create something that just seems like it works only to bring more people they can use.
Sure! Go check Riot, Free software, decentralised, anonymous (or not—You choose), works on every platform and can be brigded, integrated or use bots.
Another option would be IRC.
If You have to work in an unhealthy environment and are forced to be used by Slack, use email instead.
Or do Your own research.