Which of the following penalties involves a loss of one point value?

The penalty for hitting a cone in equestrian events typically results in a loss of one point. This rule is established to maintain the integrity of the course and to emphasize precision in maneuvering around obstacles. Hitting a cone indicates that the horse and rider did not navigate the course as intended, thereby warranting a loss of points to reflect that error.

In contrast, the other penalties involve more significant impacts on scoring or are not uniformly recognized as involving a one-point deduction. For instance, a loss of rein or stirrup can affect the rider's control and safety significantly more than a single point deduction, while overturning by a quarter could imply a more serious error in navigation that might carry heavier penalties depending on the context. Therefore, the identification of hitting a cone as incurring a one-point penalty is key for understanding how specific actions affect overall scoring in equestrian competitions.