This pledge closed almost 2 years ago
The law requires that a cyclist signal when turning. Left turns are signaled by pointing to the left, and right turns are typically signaled by raising your left arm to an upturned position. The latter makes sense for a car driven, but is unnecessary for a cyclist, and actually more dangerous given that it's not easily intuited.
The Uniform Vehicle Code in the US actually recognizes both this signal and the arm to the right signal for cyclists.
This pledge is a commitment to pointing in the desired direction when turning.