When I was doing shimush in Crown Heights over 10 years ago, I observed a certain magiha making an issue of the kuzu on the back of the mezuzah. If it was not lined up PERFECTLY (letter by letter, observed against the light) k'neged the letters of the shaimos on the first line of the mezuzah, he would mention it to the customer and say that such a mezuzah lacks shmirah and ideally should be replaced. While this magiah was / is a tremendous talmid chochom, and I learned a lot from him, I always felt that he was going a bit overboard on the kuzu issue. My sentiments were further reinforced when I could not find one Rav anywhere in the world who agreed that a mezuzah should be replaced because of a slight misalignment of the kuzu.
Recently someone from crown Heights called me and told me that he had his mezuzos checked and a magiha gave him the same shpiel about the kuzu and that he should change his mezuzos. This magiha happened to be a talmid of the first magiha I mentioned in the first paragraph. At any rate, I again called a number of heavyweight rabbanim, all who told me that this is a chumrah that is unnacceptable and misleading. I relayed this to the customer and he (rightly) opted to keep his existing mezuzos.
One of the advantages of having a system of rabanim and morei horoa (i.e. daas Torah) in established fields of halacha is to maintain a certain standard of practice that prevents deviation and misinterpretation. If every daas yochid / left field chumrah is thrown upon unsuspecting consumers, it will cause (and does cause) tremendous confusion and ill feeling that no doubt affects all involved, including other magihim and sofrim trying to do the right thing.
Comments or feedback on this thought are appreciated.