Last modified: 2013-10-28 15:07:51 UTC
The link to the image details page says "Learn more on a shared repository" (a fallback text coming from {{int:shared-repo}}) even though the repository name is set. This is quite possibly a misconfiguration with my local setup, will investigate later.
Indeed a setup issue. Apparently display name of the repo is not fetched via the API but read from the local message shared-repo-<name> (where <name> comes from $wgForeignFileRepos). Commons must be named 'wikimediacommons' in the local shared repo setup, then it will have a nice name.