There is no standard, that’s why I’m asking to make a setting and be done with it. If I choose Enter to make a newline, I expect anything else to some other action such as Submit.
It is a terrible user experience if Shift+Enter makes a newline while Cmd+Enter submits — these two are very easy to confuse between each other, and we are back to unreliable behaviour which is definitely not the “least surprising”.
It must be between A) an Enter alone, and B) an Enter pressed with a modifier key. This is the only way to distinct between a new line and a submission intention, and that will make user using the editor smooth and intuitive.
Grouping “Enter” together with “Shift-Enter” to produce a newline, and then have “Cmd+Enter” to submit — is a terrible idea imo.