From BibleGateway:
Jesus Forgives a Woman Taken in Adultery
This story, beloved for its revelation of God's mercy toward sinners, is found only in John. It was almost certainly not part of John's original Gospel. The NIV separates this passage off from the rest of the Gospel with the note, "The earliest and most reliable manuscripts and other ancient witnesses do not have John 7:53--8:11." That is, the earliest Greek manuscripts, the earliest translations and the earliest church fathers all lack reference to this story. Furthermore, some manuscripts place it at other points within John (after 7:36, 7:44 or 21:25), others include it in the Gospel of Luke (placing it after Luke 21:38), and many manuscripts have marks that indicate the scribes "were aware that it lacked satisfactory credentials" (Metzger 1994:189). Furthermore, it contains many expressions that are more like those in the Synoptic Gospels than those in John.
________________________________
Has the Watchtower Society ever taught on this passage?
Was it ever included in the NWT? If so, when was it removed?
_________________________________
As the "mouthpiece of Jehovah" I would be compelled to believe the WTS was an early proponent
of identifying this passage as bogus. It would be downright embarassing for Holy Spirit to have missed this detail.