Markdown renderer incorrectly handles single line breaks

Under typical markdown, single line breaks should be treated as whitespace (and combined with adjacent whitespace into a single space). However, in many places, RedReader simply eliminates single line breaks, leaving no spaces between words.

I noticed this issue on this post: https://reddit.com/r/talesfromtechsupport/comments/1uo1f3f/the_reports_are_all_wiggly/, which does render correctly in both the old and new Reddit websites.

From what I can tell, this only effects some posts (although this may be related to how the post was created, since Reddit's fancy editor might generate extra characters that allow RedReader to handle the markdown correctly). I haven't seen an example of this issue in comments, so they may be unaffected.

Reproduce the problem in RedReader with the linked Reddit post, comparing its rendering with the old and new Reddit websites. Trace the Markdown rendering path for posts and verify whether single line breaks become whitespace without affecting comments. Done means affected posts display separated words correctly, including adjacent whitespace handling.