Some Wikipedia templates, including Infobox musical artist, now use a module to check for parameters that shouldn't be there: https://en.wikipedia.org/wiki/Module:Check_for_unknown_parameters

That seemingly adds <span style="display:none">HIDDEN ERROR: Usage of "VALUE" is not recognized</span> when something looks wrong - but we're displaying it, e.g. http://beta.musicbrainz.org/artist/eeef4695-266c-4bf6-9697-4d0569204f7d