One of the guiding WikiPrinciples is that the plain text you type should, in general, be pretty close to the text that gets rendered. Starting from that idea, and adding that people have different preferred window widths, and that you want at least some formatting such as
A wiki is not the Web, and the markup language used will (generally) not be HyperTextMarkupLanguage (HTML). The specific markup used here (see TextFormattingRules) is designed to be simple yet powerful, aiming for a different trade-off from that targeted by HTML. In HTML, the text is often hard to find amongst the markup, but you have far more control over the presentation. In this wiki, the ideas are considered more important, and control over the presentation is minimal.
Still, many people wonder "WhyDoesntWikiDoHtml?"
If you're unhappy that this wiki's markup doesn't have feature X, ask yourself if you really need X to communicate your ideas. Chances are pretty good that you don't. Thousands of other WikiZens communicate their ideas without it.
Moved some content to AlternativeTextFormattingRules.
I like the markup used by MediaWiki (of WikiPedia fame) myself. Highly familiar to those familiar with both c2 and HTML/XML (with a bit of LaTex thrown in). All the various tricks with single-quotes works, as does the leading * for bullets (and **, *** for indented bullets). Similarily, leading #, ##, ### give numbered outlines; leading :, ::, ::: gives spaces. Leading spaces give typewriter mode.
Differences: Links must be written using two square brackets [[like this]]; CamelCase doesn't work for links. With a pipe you can have the link text different than the actual link [[like this|like that]] (which links to "like this" but prints "like that"). Certain HTML/XML markup is accepted; <b>, <i>, <u>, <tt>, etc. & displays & (all the other XML-style character escapes work as well). < and > not part of an HTML tag display as normal; you don't have to quote every free instance of < as < which is nice. Mathematical markup is done using a Tex-like markup language, with forms like \sigma and such.
Oh, and templates are a rather cool feature....