We always buy travel insurance. We got to use last May when we were suppose to be on the Infinity heading to Alaska. Instead, we were in a hospital where my DH was in a coma from a heart attack. He recovered and we have cruised since. We were able to get all our money back through the insurance with no problem at all.
However, in this particular case, I would have immediately called my CC and filed for non-performance of service against Celebrity. I would have also called my insurance company then let them all duke it out but in the end I would have expected to get back every dime I had spent.
I have asthma and at time can have a coughing jag that will make my bp and temp both soar temporarily. DH's heart meds dry his throat and make him cough. Sometimes to listen to one or the other of us, I'm sure people think we have the plague. I wouldn't expect any ticket takers to have even the slightest idea of what is the truth and what isn't medically speaking.
I have never even considered putting anything on those health forms that would indicate we have had any kind of flu, temp or whatever. I don't trust the employees of the cruiselines to have any common sense at all and this thread just shows I'm right.