[radlad]

IME, Slack is far more likely to lose my message than iMessage. I believe that's part of the point being made above.

[gmmeyer]

I've never had slack lose a message when it's up

[radlad]

That's kind of the definition of a service being up. :) I've experienced numerous "soft" outages which result in messages not sending and getting lost - and even more double sends, sometimes very distant from where the message was originally sent.

ITT: Anecdotes