[RiderOfGiraffes]

At the bottom of every page there's a link to the FAQ: http://ycombinator.com/newsfaq.html

That has the question: "What kind of formatting can you use in comments?" followed by this link:

http://news.ycombinator.com/formatdoc

That says:

  Blank lines separate paragraphs.

  Text after a blank line that is indented by
  two or more spaces is reproduced verbatim.
  (This is intended for code.)

  Text surrounded by asterisks is italicized,
  if the character after the first asterisk isn't
  whitespace.

  Urls become links, except in the text field
  of a submission.

Does that answer your question? You get a line break by leaving a blank line.