Hi,
I almost fully agree with Rowan but I also like some more semantic markup, so I introduced some techniques in the German Wikipedia with different goals:
Bewertungsbausteine - stamps to judge articles http://de.wikipedia.org/wiki/Wikipedia:Bewertungsbausteine
Datenbanklinks - links to other databases http://de.wikipedia.org/wiki/Wikipedia:Datenbanklinks
Personendaten - metadata for articles on people http://de.wikipedia.org/wiki/Wikipedia:Personendaten
You can do a lot with Templates if you describe them well because no average author understands them.
In 'de' they just invented an invisible "personendaten" box...
Again, you've lost me; for what purpose did they create this "box", in what sense is it "invisible", and how would XML/"a proper markup language" deal with the same issue?
'Personendaten' (personal data) contain machine-readable metadata on people. They are normally invisible through CSS so you have to switch them on in your Monobook.css (I'd like an easier way to do this) but you see them in article source. Karl already cited an example. Here is an english one:
{{Person| NAME=Magellan, Ferdinand |ALTERNATIVE_NAMES=Fernão de Magalhães (Portuguese), Fernando de Magallanes (Spanish) |SHORT_DESCRIPTION=sea explorer |BIRTH=Spring 1480 |BIRTH_IN=Vila Real, Trás-os-Montes, Portugal |DEATH=April 27, 1521 |DEATH_IN=Mactan Island]], Cebu, Philippines }}
The data should be moved to a seperate metadata page with all the other metadata stuff.
greetings, Jakob