On https://www.wikidata.org/wiki/Property:P8408 the formatter URL https://kbpedia.org/kko/rc/$1 has normal rank as formatter URL (P1630), with https://kbpedia.org/knowledge-graph/reference-concept/?uri=$1 having preferred rank, and deprecated rank as formatter URI for RDF resource (P1921); despite this, in the examples of the property and in all items https://kbpedia.org/kko/rc/$1 still appears as formatter URL, seemingly stuck.