There's always been a lot of discussion about page metadata and microdata but never any conclusion.
At some point I was tricked into believing that it.source used microdata (https://it.wikisource.org/wiki/Progetto:Qualit%C3%A0/Semantizzazione ?), but clearly it doesn't. https://www.google.com/webmasters/tools/richsnippets?q=https%3A%2F%2Fit.wiki... Compare: https://www.google.com/webmasters/tools/richsnippets?q=https%3A%2F%2Fcommons...
Just make all those damned templates output something useful in the HTML!
Nemo