No, you're not likely to be stranded but it can happen. October can be a changeable season and if a storm comes up and the sea gets too rough, the boats won't run. Will the hotel on Capri be understanding? Hard to say. It's not high season so it's probably not like they could have sold the room many times over but held it for you. I would email the hotel and ask them what their cancellation policy is and what specifically they will charge if you are unable to get to Capri due to the weather.

Sorry for not really paying attention Jean, I agree with you!

Thanks for the good advice Grinisa.