Having [someurl] turn automatically into [1] is an
elegant
solution. The heedless coder leaves a clean external link
behind, not a godawful URL, which might be two lines long and
rife with % signs, and the careful coder has a choice of simple
footnote or prettified link.
Yeah, that's a pretty good argument.
How about this:
[
http://www...] renders (a href="http://www...")[1](/a) with
autonumbering, [
http://www...|text] renders (a href="http://www...")
text(/a) (the pipe can optionally be a space), and [
http://www...|]
(note trailing pipe) expands to [
http://www...|www...] ?