query: select distinct ?item ?itemLabel ?example1 ?example2 ?facebook1 ?facebook2 where
  {
  { ?item wdt:P2002 ?example1 . ?item wdt:P2002 ?example2 . 
    filter(?example1 > ?example2) . 
    # item has two values for example account
    filter((lcase(?example1)) = (lcase(?example2)) ) . }
    # but they are the same case-insensitive text
  
    union
  
  { ?item wdt:P2013 ?facebook1 . ?item wdt:P2013 ?facebook2 . 
    filter(?facebook1 > ?facebook2) . 
    filter((lcase(?facebook1)) = (lcase(?facebook2)) ) . }
    # same but for facebook
  
    # as of 2019-03-19, 176 example and 27 Facebook
    
    # nb please do *not* fix automatically by removing entries without checking them first
    # as one value may have key qualifiers (follower count, verification, sources, etc)!
    
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
  }