That said, Twitter and Slack are very different beasts. There is not nearly the same network effect to keep teams from switching to a competitor... except to the extent that 3rd party products integrate with Slack's API...
Their potential killing of the APIs won't affect if I use Sikuli to automate it.
The only way you'd be able to detect that is by measuring the amount of ms between clicks. And that's defeatable by adding in a random range of 0-300 ms per click. And send the data to a private IRC room. Node-Red can easily handle the data from there.
Now, it looks just like a human.
I've seen a growing number of people actively moving away from Slack or complaining about it due to these issues. How can Slack fix that? Close off an API to stop hiving off users? Well the explicit intent of this approach is to use both tools so it doesn't seem like they lose much.
Either way; I'd argue that a rational company would look at why it's customers were doing these things and then either a) add that feature to the product or b) let things alone.
Slightly different if it's an "export your Slack chat to A.N.Competitor".