Just some notes to help with working out which names are duplicates or not.

Ann Yu and Anne Yu are different people. Ann recently changed her name to An, so now both variants are recorded as An (formerly Ann).

Jin Kim and Jisun Kim are different people. 

The following are correct names with their variants that need to be changed.
Keith Rodgers (Rogers)
Emily Allen (Allan)
Joanne Thakker (Jo)
Edward Quill (Ted)
Steffan Sinclair (Stefan)
Natasha Gale (Natasia Gail)
Alex Hayr (Hayre)
Jisun Kim (Jsin)
Richard Oatham (Ricky)
Nicole Morrall (Nicky, Morell)
Janet Robinson (Jan)
Susannah Williamson (Nee Davison)
Andrew Bell (Andy)
Eszter Le Couteur (Le Couteur-McComb)
Georgia Steel (Georgina, Steele)
Adam Maha (Mahar)
Madison Gilling (Maddie)
Matthew Gough (Matt)
Alexandra Vincent (Alex)