In most sites I've looked up so far (many languages Wikisource, Wikiquote, Wikibooks), except Wikipedia, have now have this strange bug.
Steps to reproduce:
1 - Look at any page that doesn't have interwikis, for example EXAMPLE 1 or EXAMPLE 2 or EXAMPLE 3, using Vector skin. At the bottom of the left panel, it should be a "div#p-lang " with a link for adding new languages. Now it doesn't
2 - Look now at EXAMPLE 3, using monobook. The bug resolves
3 - Now add some mock link (as in here). The section appears normally.