Really appreciate BruceK posting on this very unfortunate but instructive incident. There are several take-aways from reading the inquest report, even if only when considering the purchase of a newly-built recreational vessel whose designer and builder represent it as safe.
Then there is the marketplace of used boats. Like humans, boats gain weight as they age. I don't mean to suggest that wet deck or deckhouse cores are enough to destabilize a boat that was stable to begin with. As the inquest states, that should not have fatally compromised the Eliza 1. However, it can be another straw on the camel's back. Over time, most of us add things to our boats, whether it be tools, accessories, systems or enhancements to the deckhouse / flybridge. As the decades pass and weight increases above the original center of gravity, the location of the CG follows. Typically the process is gradual enough to go unnoticed, until external forces like wind, swells, or an unusually large number of passengers converge at the wrong moment.
Whether it's our own boat or one we're considering buying, one of the lessons here is that even if a vessel floats on her lines at the dock, ultimate stability cannot be taken for granted. Even experienced boaters such as Alan Beeby and his son Scott seemed to have been confident of the Eliza 1's stability, although the inquest report does say this: "According to Scott, he observed Eliza 1 to be immaculate and well cared for, however Scott says he did notice the vessel listed slightly as they stepped aboard" (p. 11, paragraph 37). Many of us, including me, might have taken a slight list upon boarding as evidence of nothing more than some initial tenderness.
If there is any cause for question, some sort of fresh stability assessment would deliver peace of mind, at a minimum.