Where is the markup language defined?

The markup format used is called Markdown, and is rather simplistic. It's useful to learn since it's used by the various Wiki systems, Weasyl, Reddit, and a smattering of other sites. Weasyl's super nice in that their system actually has a preview so sometimes I'll load it up real quick just to make sure my post is formatted correctly when I need to post somewhere that can't be bothered with a preview system *cough*reddit*cough*

Unfortunately, that is a problem. There are dozens of flavors of Markdown, some with their own exclusive features. There are also some general Markdown features that are slightly broken here, such as the use of @ and # in mentions and hashtags respectively, and HTML parsing is disabled as I recall (which breaks the MD standard). There really needs to be a solidified reference for FN's flavor of Markdown.

Ahh! I didn't even think to try Wiki-ish Weasyl-ish Reddit-ish language. *facepalm* Thanks!

And it sounds like there's some "cooking" yet to do with the parser, but that's beta for you. ^__^

Aha, I found that there's a little "M" button in the bottom right of some text entry fields. If you click that (sometimes takes a few tries, at least in Firefox), a pop-up appears and displays the codes you can use. It goes away when you start to type in the field, though, which is not very handy. So, two windows or a screenshot or something is what you'll want 'til you get used to what's available.