Would there be problem with bending the ground rod of a residential
transformer at the half-way point at installation? (i.e. the eight
foot rod would only go four feet underground, the other four feet
would be horizontal) If so, why?
Yes, there'd be a problem.
Why? Because it would violate code, for one. For second, if you've only
got 4 feet of it "down where it belongs", then you're probably not
hitting the permanently moist earth that a ground rod is supposed to be
embedded in, which increases your ground resistance, and reduces its
effectiveness. Exactly how much of an effect is dependent on too many
variables for me to make a prediction, but the effects are pretty well
guaranteed to be "not on the plus side of the ledger".
Just sink it the way it's supposed to be sunk. You (and anybody that
ends up with the building after you, if it survives that long) won't be
sorry you went to that small amount of extra effort.