Don't give up the dream of ImmersiveHypertextEditing just because HTML forms and plain text email are, as of 2003, the only ubiquitously deployed collaboration tools.
This business of using [1] style footnotes with URIs at the end of a plain text mail message is one thing, but don't do that in HTML, please. HTML is rich text. Just use links.1
And let's keep the in-your-face URLs to a minimum, OK? Clean them up when you see them in this wiki.
PoorMansHypertext comes up a lot. In-program documentation like javadoc, doxygen, perl's pod, and python __doc__ strings all seem to develop something similar (e.g. epydoc). It's a shame they're so incompatible and yet generally so similar.
Where do non-XHTML XML documents fit into the picture?
MoinMoin has a macro to make this easy. Are such macros an advantage of PoorMansHypertext? No, they work against the principle of least power; see also: On Formally Unconvertable Document Formats.
1 Within a page, you can even make your links look like footnotes, if you want.