(1) When a person stands on the horizontal platform of the escalator, as the escalator rises at a constant speed, he is subjected to a balancing force, but not to the horizontal force. Gravity and the vertical supporting force are a pair of balancing forces; Old friends * * * are influenced by two forces;

(2) Mechanical energy includes kinetic energy and potential energy. In the process of people rising at a constant speed with the escalator, the mass and speed remain unchanged, so the kinetic energy remains unchanged; Moreover, the height of people becomes larger, so the potential energy of gravity increases; So the mechanical energy is increased.

So, the answer is: (1) two; (2) increase.