RDF Import form relies on $rogAllowRemoteEdit being set, and does not give proper error message

Trying to import the sample turtle data on Special:RDFImport ... nothing happened after clicking Submit ... or, the page re-loaded, but no message indicated what had happened, if anything.

Turned out that write access was not aquired, because $rogAllowRemoteEdit was not set. But that should not be required, since that is meant for remote SPARQL editing.