I'm not sure if this is something fixable on Staff's end, but single-line breaks keep tripping me up: the post looks fine in Preview, but without the double-space or <code><br></code> tag, the text all truncates to a single line once it goes live. As someone with very little experience in markdown, this is going to be a bane unless/until we can edit comments.
Yeah, this is an annoyance for us, too. It's one of those things we've noted, but got back-burnered for larger tasking. Thank you for the reminder. I'll bump it back up to a higher priority to fix.
So, after a little research, Markdown will insert a line break if a line of text ends with two or more spaces. For example:
This is a line of text.[space][space]
This line will be on the next line.
I tested it on the dev server, and it displayed properly doing that. Pain in the tail, for sure, and I'm going to look to see if there's a more natural way I can make single newlines work. But, until then, that would be the way to make Markdown put in a linebreak.