This plugin is excellent and very stable. I have used it in the past and I"m now using it on a new project. My thanks to Mark and the other contributors!
The only thing I would like to see added is named footnotes, as in MediaWiki/Wikipedia. This would save from repeating all the footnote text each time the footnote is used.
Here's how it works in Mediawiki/Wikipedia, although another notation may be better for this plugin:
The lyrics are great.<ref name="hello">You say goodby and I say hello</ref>
There are some great lyrics out there.<ref name="hello"/>