I’m not sure which of the copy actions you were using, so I just went with a version of the simplest one for you. I’ve incorporated adding the standard Markdown double spaces to the text the action processes. It will leave the original draft untouched.
Generally though, getting into the habit of using double spaces and blank lines when working with Markdown will make your Markdown syntactically correct for your needs and more transportable. Not every system that uses Markdown will offer the same affordances as Drafts and Markdown continues to surface in more and more places as a text entry option.