Last modified: 2013-11-12 16:29:30 UTC
"It is possible to paste an accurate Commons media filename like File:filename.jpg into a property that accepts that type. However, it does not strip the "File:" prefix, so the URL created is invalid: it has the form commons.wikimedia.org/wiki/File:File:filename.jpg." (reported at http://www.wikidata.org/wiki/Wikidata:Contact_the_development_team#media_data_type_URL_problem)
Since the implementation of validators, it is no more possible to paste a prefixed Commons link. Allowing prefixed Commons links would be an enhancement.