[wp-docs] Language-linking in the Codex doesn't work

[Hans Engel]

I used to edit Wikipedia a lot, and I remember one of its most
user-friendly features was to provide links to the same article in a
different language.

This could be done by placing something like this at the bottom of the
article:

[[de:Hallo]]

This would add a link in the sidebar of the English 'Hello' page for
German viewers.

I tried inserting this in my pages, but it didn't work. Is this feature
deliberately disabled, or is it a bug?