Just a quick correction. AC797 wasn't actually caused by careless smoking or problems with the lavatory smoke detectors.
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Many changes were made as a result of this accident (both to prevent ignition, combat fires and aid evacuation), but those all had to do with the physical characteristics of the aircraft (flammability standards, firefighting equipment, training, smoke detectors, emergency lighting, etc.). The no smoking ban (and no tampering announcements) were not a direct result of that incident.
I was under the impression that AC797 directly led to the installation of the smoke detectors (as you said) and was also used as ammunition to justify the later smoking bans even though there never was any evidence of tobacco having anything to do with the incident. If I remember right (I was a kid living in Dayton, OH not far from Cincinnati), there was rampant media speculation that a cigarette in the trash bin was the cause even though that was not the conclusion of the investigation. I'm not aware of any particular incident that led to the no tampering/disabling/destroying announcements other than a general history of (non-fatal) lav trash bin fires from smokers, but it seems a natural extension of installing smoke detectors to become concerned they aren't tampered with.
If there was a specific tampering incident that led to those announcements, I'd be interested to learn about it.
Either way, we should cleanse ourselves of no-longer-relevant intellectual junk such as these announcements that clutter our lives. I'm highly confident that attempted cabin smoking in 2011 could be adequately addressed by crew (and pax) admonitions to anyone who tries to light up and the quite tamper-resistant detectors that are installed in the lavs.