Several decades ago, users in Wikimedia may set their "real names" (which in many cases is set to actual real names) and they are stored in user_real_name column. This feature is later removed, but real name already set remains in database and are visible in replica (this column is public) with no way to remove. Therefore I propose that this field should be blanked in all Wikimedia wikis since they may infinitely contain PII.
In most Wikimedia wikis this field is sparsely used; but in Wikitech almost every user has a real name.