[kijin]

There are "extra" versions of Markdown that can be configured to respect literal line breaks. But if you rely on that, your text would not be compatible with other Markdown parsers.

Markdown's default behavior of disregarding line breaks has two benefits: (1) you can keep your lines short without breaking paragraphs apart, and (2) putting each sentence (or long clause) in its own line plays very nicely with version control systems.

[mcantelon]

Yeah, respecting literal line breaks would break some things, but simply replacing the two spaces at the end of a line with something visible (maybe two underscores if that doesn't break something else) should work.

[fiddlosopher]

Pandoc's extended markdown allows you to use a backslash at the end of the line to indicate a line break. (Think of this as a backslash-escaped newline, if you want.)