That works for email, but less-so in Slack or IM in general. I did once play with a hacked-on delay-send setting, but any delay must be long enough to allow yo

That works for email, but less-so in Slack or IM in general. I did once play with a hacked-on delay-send setting, but any delay must be long enough to allow you to register making a mistake first, e.g. 3 seconds) but when it's that long it ruins spontaneity and the rapid back-and-forth experience when chatting away - in that situation I definitely prefer send-on-button-up, not send-on-button-down.