Markdown isn't plain text, however - while annoying, you could achieve the desired formatting with markdown both in plain "unrendered" mode, and in eg: html, by appending "<space><space><enter>" for forced linebreaks. There's no equivalent AFAIK for hn markup, you'd have to use a pre-block:
- pest
- cholera
pick one.
I believe the choice to translate single-enter to a space that can be reflowed is actually based on among other things email-formatting: https://tools.ietf.org/html/rfc2646#section-4
I suppose the reasoning for not sticking with "<space><cr><lf>" for soft breaks, and "<cr><lf>" for hard breaks is that plain text on *nix uses just <lf>. So either most people would get ugly <cr>-marks and/or inconsistent <cr><lf>s in their README.md-files, or something other than rfc2646 was needed.
I suppose the reasoning for not sticking with "<space><cr><lf>" for soft breaks, and "<cr><lf>" for hard breaks is that plain text on *nix uses just <lf>. So either most people would get ugly <cr>-marks and/or inconsistent <cr><lf>s in their README.md-files, or something other than rfc2646 was needed.