Facet labels are double-translated in FacetapiDependencyFacet::getEnabledFacets()

The $facet_object['label'] variable is passed to t() in the FacetapiDependencyFacet::getEnabledFacets() method, however the label should already have been passed to t() or translated by the i18n module in it's hook_facetapi_facet_info() implementation. See Facet API's core facet definitions for an example. In addition, according to the API documentation you should avoid passing dynamic variables to t() unless certain conditions are met, in this case none of them are.