Last modified: 2009-04-23 22:23:11 UTC
Setting the title in [[Special:ExpandTemplates]] to something like "Talk:Foo/bar/baz" and then entering [[../foo]], should produce a link to [[Talk:Foo/bar/foo]]. This works on normal pages, but not on the special page.
Works correctly for me.
Created attachment 6052 [details] Screenshot I ain't seeing it!
Subpages are not enabled in the enwiki category namespace. You will get the same output if you try it on an actual category page. Relative links work fine in Special:ExpandTemplates for namespaces where subpages are enabled.