I am also sensitive to the lingering odor of cigarette smoke, yet have rarely noticed it in cruise ship cabins. There was one instance, but that was many years ago, in which the prior occupants were heavy smokers, yet cleaning methods are much improved since then.
There have been few times I've noticed the odor of cigarette smoking from an adjacent cabin, yet these were on older ships.
You raise an excellent point, though. NEVER trust a cruise line agent, as it's possible that this person has never been a passenger on one of the line's ships. This goes for just about any topic. Checking the cruise line Web site is an excellent idea.
That said -- I updated the Cruise Line Smoking Policies thread
in our FAQ section to reflect a few changes and to also add Seabourn. So, thank you!
You're going on a fabulous itinerary not offered by many lines. I wouldn't cancel due to this.