That's ridiculous, right?. Cmd/Ctrl-z has a defined function. Slack is hijacking that because they've decided that decades of established patterns are wrong and creating another one-off for their very specific use case is the right thing to do. The hubris...

It's not really that radical of a thing to do though. Word has the same sort of behaviour except utilising backspace. If you type " - " in word it creates a bulleted list, hit backspace once and you get the literal text you entered.

I'm not entirely sure which is the less-worse option here but at least it's not a wildly new concept, just a different button.

There are other products out there that put automatic changes on the undo stack. I regularly encounter this behaviour in Visual Studio: pasting code in the editor is decomposed into pasting text and reformatting it. So the first Ctrl-Z reverts the code to the exact text you copied. The second Ctrl-Z will remove it.

Interestingly, if I do that, it will then send it unformatted. I want to format in the actual chat, just not in my input.