Have you ever read Hofmann's book, "LSD, my problem child"? He did have a bad experience on that first trial, but he took plenty more LSD over the years. Not only that, he isolated psilocybin and psilocin by ingesting the different fractions obtained from mushrooms to identify the active components. That was the way that he beat everybody else to the identification. The others were trying to use lab rats to assay during purification.
As far as Shulgin, yes, he did things right. That's my point. If you read Pihkal he describes his method, called the "double conscious" technique. Real HPPD sounds a lot like schizophrenia from the symptoms that I have heard, and some people are going to be susceptible to schizophrenia. On the other hand, the HPPD that comes from frying your brain is just that. But a lot of the symptoms that people describe here as HPPD are common visual phenomena such as phosphenes and floaters that have nothing to do with psychedelic use. Once you have experienced psychedelics, you tend to take more notice of sensory phenomena that other people overlook.