See for example https://tools.wmflabs.org/ldap/group/archiva-deployers
Apparently this is Milimetric in the list, which displays right on other ldap lists he's on as in https://tools.wmflabs.org/ldap/group/wmf
Wondering if he was added with a bad format via LDAP (tempted to tag with SRE but I prefer someone to see if there's anything wrong in the coding of the tool first).
He's not the only example. Multiple instances of <unknown users> can be found on the other listings.