Comments use Markdown, not html. The Show Help button at the lower right of of a comment box will give you details. As I recall, two spaces at the end of a line are a hard return-- it's been a while since I had to wrestle with how a list or a poem would appear.

Articles use html, sort of. There's an html button at the top. If you copy and paste from a word processor, you might get inconvenient formatting.

I don't like this system, but the only thing worse than this system is having to try to guess how it works.

[comment score below threshold] I think that's anything with -3 karma. You can see the article/thread for free by clicking on the link, but if you reply to anything on that thread, you lose 5 points.

[continue this thread]-- LW has limited nesting of comments, so this link will start a new window. You will lose your pink borders on the old window if you left click, so I recommend using a new tab for continuing threads. You get the option of a new tab by right-clicking on the link.