In text boxes in some applications, enter submits the entered text, and ctrl-enter forces a newline (not at my computer, but I think Slack does this). In others, it's the other way around (pretty sure GitHub does this for comments).
I don't know how we got here and I don't know how to fix it, but "bring back idiomatic design" doesn't help when we don't have enough idioms. I'm not even sure if those two behaviors are wrong to be inconsistent: you're probably more likely to want fancier formatting in a PR review comment than a chat message. But as a user, it's frustrating to have to keep track of which is which.
I don't know how we got here and I don't know how to fix it, but "bring back idiomatic design" doesn't help when we don't have enough idioms. I'm not even sure if those two behaviors are wrong to be inconsistent: you're probably more likely to want fancier formatting in a PR review comment than a chat message. But as a user, it's frustrating to have to keep track of which is which.