#GNU Sed, 33

Score includes +2 for `-rn` options to sed.

This is almost a direct port of @FryAmTheEggman's [Retina answer][1]:

    :
    s/(\w)(.*,.*)\1/\2/i
    t
    /\w/Q1

[Ideone.][2]


  [1]: https://codegolf.stackexchange.com/a/74183/11259
  [2]: https://ideone.com/ANy32v