I'm not sure about the 'newline-is-linebreak' idea. I can see how for user-submitted content it's there for people that have never used Markdown before, but I like to wrap my text to 80-characters when I'm composing so that it's not stretched across the screen.

I do this because I don't know of any way in vim to set a 'soft word wrap' so that lines are soft-wrapped at a specific column instead of just at the max width of the buffer. (Creating a fake vertical split is not what I want.)