You answered my question in part (see below) but can you change my ticket to join at Taormina instead of Catania?
Original question: I have seats booked on the train from Catania to Naples but it would be more convenient to join the train at Taormina - do I need to change the ticket?
Answer: if you do not board at the original station of your ticket the conductor has the right to consider you a no show and may sell your seats. The choice is yours but you may board and forced to buy another ticket