I also sent a LOT of Slack messages prematurely for the same reason. Used to it now, though. The more an interface emphasises the single-line nature of a text input, the better. Multi-line should never submit on enter, single-line always should.

Same, but it's configurable in slack so now I have it configured the Enter inserts a line break and Cmd+Enter submits the message

while I haven't changed it, it seems that you configure that behavior in the current version of Teams (Settings > Chats and channels)

It's because enter does different things at different times in the exact same text box.

Write a code snippet/block text. Does [enter] insert a newline, exit the block, or send the message?

What about in a bulleted or numbered list?

And my 2 biggest pet peeves with MS Teams:

1. trying to edit the first letter in a `preformat block`. It's not possible. It will either exit the block or go to the second letter.

2. Consistency with bold/italics. Bold a selection of text. Then backspace once. Are you going to write bold or normal? What does ctrl-B do? Anytime you backspace into a bolded section, it will convert your editing back to bold, and you cannot disable bold.

I have a very small Kevin Bacon number to the "guy who runs Teams". The message from them is "please use the built-in feedback tool to tell us about these things".