A daily minor annoyance: #GFM (GitHub Flavored Markdown) breaking standard #Markdown behavior by rendering single newlines as <br>.

If you're used to formatting plain text with hard wraps for mailing lists, you know the pain. You type up a perfectly readable 80-column text block, hit submit, and realize #GitHub has turned it into a jagged mess of arbitrary line breaks. I really miss standard Markdown paragraph collapsing in issue trackers.