What is the ruling on moving the finger or extending it forward during the Tashahhud, and does anything result from not doing so?

Pointing with the finger during the Tashahhud is recommended by the Four Imams. The disagreement lies in the specific point at which the pointing is recommended, and in the permissibility of moving the finger along with the pointing. There is no blame upon one who omits the movement or the pointing, because this is among the Sunnah acts of prayer, not its obligations.