Who says, “The Lord rebuke you Satan”?
And the [angel of the] Lord [yhwh] said to Satan, “The Lord [yhwh] rebuke you, Satan! The Lord [yhwh] who has chosen Jerusalem rebuke you! Is this not a brand plucked from the fire?”
~Zech 3:2
[angel of the] : Addition made into the NWT. Any additions added in brackets [] (according to the Forward in the NWT) are to clarify a passage and not add to the meaning of a passage. Does the addition of the phrase [angel of the] change the doctrinal meaning of the verse? It certainly does in this case. Without it, we have the Lord [yhwh] saying to Satan, “the Lord [yhwh] rebuke you”. With the added phrase, we have the angel of the Lord saying, “the Lord [yhwh] rebuke you.” In the verse above, there are two (2) distinct persons of yhwh, but in the NWT, one person of yhwh is removed.
One yhwh is the eternal Son of God, the pre-incarnate Christ. This would go against the Watchtower teaching that Jesus is "a" god rather than God. Therefore, the addition of the [angel of the] to support their doctrinal bias and remove the reference to a second person of yhwh.