I don't understand the love for markdown. The problem is it ignores a single line break. Comments on hn and reddit do that too. Result: people posting a list of things intended to be one per line, instead become concatenated on 1 line with spaces. I know there is a way, two spaces at end of previous line. That method is hard to maintain if editing, has nothing to do with plain text, easy to forget, and most don't know.
It should turn a line break into br, then markdown would be alright.
With an 's#\n#<br/>#g' substitution you now have to choose between readable source text (lines < 80 characters) and responsive rendered HTML (lines don't break until boundaries).
The problem is many input fields in websites trending to use it now. I think BBCode was more suitable for that. Markdown is easier than BBCode on one hand, but the newline thing ruins it for simple replies to posts.
It should turn a line break into br, then markdown would be alright.