[out:xml][timeout:3600]; ( way(918935027)['subject:wikipedia'='Celtchar']; ); (._;>;); out meta qt;//['malformed secondary wikipedia tag - for subject prefixed tags']
JOSM Wikipedia plugin
Note to self: online version hosted at https://matkoniecz.github.io/OSM-wikipedia-tag-validator-reports, files are stored at https://github.com/matkoniecz/OSM-wikipedia-tag-validator-reports.