I don't think it's merely pedantry. The stakes are being upped as to what constitutes visibility, and yet cyclists are not becoming more invisible. What people are actually saying when they say that they cannot see you is "I would like you to signal your presence more emphatically, so that I may exercise a lower level of observation and care, and a higher level of speed." Now it happens that I think a ride leader is being somewhat negligent if she has allowed a group ride to end up with no lights whatever in a reasonably predictable fog, but I think that's a fairly unusual situation. A rider or two being caught without a full set of working lights is, however, a reasonably common and understandable occurrence, and is exactly the sort of thing motorists ought to be looking out for.
Yes. And no. Up to a point.
What you say here fits well with your earlier writing on this thread: Driver, cyclist or astronaut, every road user should make some effort to be visible and no road user should be travelling at a speed exceeding that at which they can respond safely to possible incidents or unpleasantness.
However, I disagree (predictably) with what looks slightly like a generalisation (shown in bold above). Ever since the early days of the M25, when swathes of Hollywood fog blotted out the section past Sevenoaks yet still cars whipped past at 70+, I've been horrified by the ability of some motorists to imagine they have X-Ray eyes. It still happens and the malefactors are more often (in my experience) motorists than cyclists.
But... Most motorists I know do not look to other road users to increase their own visibility so others can exercise less care and give it more welly.
It may seem like that sometimes.
Both as a motorist and a cyclist, I've been surprised at the 'invisibility' of some other road users. I don't get involved or offer advice, but I notice these things as we all do. When I fail to see another road user as early as I'd like to - and where this is in part because he or she is poorly lit - my response is not that they ought to light up so I can be less observant and make faster progress.
Perhaps some people respond as you suggest to poorly lit cyclists, but I'd wager that most are concerned (as johnnyh seems to be) for their safety.