I guess to follow your opinion, anyone who ever soaked a stamp off of an envelope in tap water would need to disclose that it has been subjected to a chemical since a lot of places have highly chlorinated or other chemically treated water. After all chlorine is a bleach and could attack the ink or the paper just like Acetone, only a little slower. So in that vain, any used stamp not on its original envelope must be considered a restored stamp. I wonder how the stamp community would react to such a statement.
Good thing the art community doesn't follow this thinking about conservation vs. restoration. We wouldn't be able to see a lot of the masterpieces.
That is not what I said and taking the discussion to reductio ad absurdum is not helping anything.
Would you want to buy a stamp that had been restored without disclosure? Don
Edit: If you had a nice bronze sculpture, dusting it with a rag is fine. But whipping out the polish and you are making changes that impact its value. If you own a rare original vintage car, you would want to keep it in its original condition and not restore it if you want to maintain its value. yes, you could do a frame off restoration, and probably make owning the care more enjoyable, but you then would not offer it for sale as an original car.
Regarding "reductio ad absurdum", you started that by comparing my mention of library books dealing with cleaning soiled stamps to books dealing with bomb making, and furthermore that stamps that have had their watermarks checked should be declared as chemically restored when selling. In my opinion both are absurd and not helping with the topic of what can be done to remove or clean tape residue. I am obviously not the only person who has encountered this problem and this topic should be informative as to what people have tried; what works and what doesn't; and finally did it have a negative affect on the stamp or not.
Regarding your question if I would want to buy a stamp that has been restored without disclosure my answer is - it depends. If the restoration involved reperfing, regumming, adding a perfin, or altering it to a more expensive stamp, the answer is No. However, if the stamp has been subjected to a watermark fluid or soaked in a fluid to remove a stain without affecting the original appearance or colour of the stamp then the answer is I wouldn't expct that to be disclosed.