You can use the following codes within comments:

Code	Result	Annotation
[i]italic[/i]	italic	Italic fontface
[b]bold[/b]	bold	Bold fontface
[url]http://www.janthor.com[/url]	http://www.janthor.com	Hyperlink
[url=http://www.janthor.com]my homepage[/url]	my homepage	Named hyperlink
[img]http://www.janthor.com/favicon.gif[/img]		Image
[e]Auml[/e]	Ä	Named Unicode entity reference
[e]#196[/e]	Ä	Numeric Unicode entity reference
[quote]Quote[/quote]	Quote	Indented text with border
[spoiler]Spoiler[/spoiler]	Spoiler	Text which is invisible unless marked
[tex]x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}[/tex]		TeX fragment as bitmap image
[code] def func(x):     print x**2 [/code]	def func(x): print x**2	Formated text with significant whitespace (for source code)

I can add more codes, if you need them, provided they can be implemented as simple regex substitutions.