There is a huge difference between the so-called "stage 1" mods done by most owners (and heavily promoted and sold by H-D and their dealers), and the major internal modifications done by some. Someone doing simple pipe, air cleaner, and tuning device mods shouldn't have to worry that these minor things create a loophole for an unscrupulous manufacturer to avoid responsibility for p-poor quality. If a Harley-Davidson motorcycle is so poorly designed and manufactured that it cannot tolerate the installation of a set of pipes and air cleaner, I suggest folks need to know that up front and then refuse to spend another dime with that company. On the other hand, anyone who does serious internal mods to significantly increase power should do so with the knowledge that they are taking a risk. If they want 130 hp and torque out of that engine, they will need to be intelligent enough to beef up the rest of the drivetrain. If they don't and it fails, they need to suck it up and admit it was their own fault, not Harley's.
All manufactured items have a certain failure rate, since nothing made by man is perfect. As long as that failure rate is small, and the manufacturer is quick to stand up and fix the problem, most people can accept the occasional failure as a normal part of life. However, when that manufacturer tries to duck it's responsibilities by blaming the customer, especially when they know their product has a real problem, it is totally justifiable for that customer to pitch a bitch, sue the bastards, and spread the word far and wide. If H-D and it's apologists don't want people to bitch, I suggest the answer is to spend more time fixing quality and design issues and less time blaming the customer for known product deficiencies. JMHO
btw, the fact that the MoCo eventually makes a repair after all their arrogant posturing and finger pointing doesn't make it all better. The customer experience shouldn't include being insulted and threatened at the whim of some ignorant corporate jerk clerk.
Jerry