1st:
Typically I use [[w:de:pagename]] to access the german wikipedia.
This link is expanded to
http://en.wikipedia.org/wiki/de:pagename which
is redirected to
http://de.wikipedia.org/wiki/pagename and works well.
There's another shortcut 'de' in interwiki.sql which I want to use and
which should be expanded
to
http://de.wikipedia.org/wiki/ (the last URL above).
When I use [[de:pagename]] to link to the german wiki no link to the
foreign page (empty string) is shown in my wiki.
Maybe it's appearing on the left sidebar? Use [[:de:pagename]] for an
inline link.