100% +1 on this. It's unacceptable IMO that this feature request is 4 years old. It's not that much more effort to click `send` manually. It prevents such embarrassment.
Since half the time I'm using the conversations box for email (which does not auto-send upon "return") and half the time for chat, the muscle memory causes so many half-chats
Please fix this, It is such amateur hour to have this feature work like this- the enter button should not actually send the message - LinkedIn fixed this on their site 10 years ago