Yet in 1926 and 1952 many more people were electrocuted at home than were killed on railroad tracks. Electricity was an invisible killer and many products and electrical systems were of unsafe designs.
In old commercial/industrial areas, yes. But in residential areas, no. Home appliances are intermittent in operation. 'home wiring of many different vintages and states of repair on the local grid' can not cause a DC offset problem.
Yes, there are two PhD's (in other fields) both skilled in writing long impressive papers. From time to time they write audiophile papers and blogs. They start from a conclusion and only examine evidence that supports their conclusion.
That's exactly how I would expect a DC offset problem to occur. It takes some using a significant amount of power to cause a DC offset. Not many items in a residential area do that for long periods of time. For the most part, these items have to be powered from the same utility power transformer.
And then you look at the current waveform at the AC input of a power amplifier and you wonder what the sine wave fuss was all about. The current waveform looks more like a square wave than a sine wave.
In a residential environment, there are few appliances capable of causing a DC offset that operate 24 by 7. So most DC offset problems should come and go, yet we don't read about audiophiles noticing this on/off situation.
One neat thing about some DIY 'DSP' crossovers is, you can program different crossover setups in as scenes. Then have someone else select a random scene. Then do your listening tests (in effect a blind test).