Thanks for writing this. There's a lot to think about here, but just for starters, your very first paragraph finally helped me to understand what failure of clarity on my part led to the hostility that we've been going back and forth with this whole time. So in the interest of improving that clarity, let me try to rephrase my original comment about crackpots to do a better job of conveying what I intended:

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If your mental model of "the set of people who publicly discuss science" doesn't include "There exist a whole lot of crackpots out there", your mental model of scientific discourse in our society is wrong. The odds of radical new ideas being crackpottery are far greater than the odds that some unappreciated genius has upended the well-tested laws of physics.
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I'm not sure whether it was carelessness or generosity that led me to use the term "the scientific community" in a way that included those working at (or beyond) the far fringe of respectability. On reflection, I think that I've done them that courtesy before; I'm often careful to specify a label like "mainstream" when I intend a more narrow definition of "the mainstream scientific community". My comment "Believe me. I get their emails." was very much meant to refer to the non-mainstream theories that folks out there seem to regularly send to active physicists in any related field (not as a backhanded slap at the handful of professional peers and colleagues who occasionally write to me). So from my perspective, I haven't made any shifts in intended meaning over the course of this conversation that would merit your signposts, but I can definitely see how my words could have given the other impression. (And now you get to judge whether I'm piling lies upon lies in a scramble to retract a broad insult to my peers, or whether I've been expressing a consistent belief system this whole time. Darned if I know any way to make that judgement easy for you.)

As for your broader points: One of the things that troubles me in the discourse between professional scientists and the public is that it's painfully common for us to wind up disappointing the very people who are the most fervent supporters of what we do. This is no doubt a reflection of your UR-FACT. A scientist who gets gleefully excited about an unexpected discovery or a strikingly elegant theoretical model is still constantly aware of the tentative nature of science: her enthusiasm is a measure of how rare even the possibility of transformative progress can be. But when that enthusiasm spills over to the public at large (by whatever channels), most listeners don't have the training and experience to recognize just how tentative the underlying idea inevitably still is. So when, nine times out of ten, the early promise of the discovery either fizzles or gets mired in technical details with no clear end in sight, the science enthusiasts in the public wind up feeling betrayed. (Even mundane things like the seemingly constant flip-flopping of nutrition warnings is a part of this.)

I don't know how to fix this. As you say, it may be truly impossible, though I'd like to think that better early and ongoing education about the process and nature of science could help a little. But I think that's what is behind my attempts to dial back the enthusiasm I see for this EM Drive work. What they're claiming is something that so many of us long to be true! (I certainly wish it were, both for the thrill of the new physics to explore and for its impact on the future of humanity.) But this isn't even a case where justified scientific enthusiasm has wound up being oversold to the public: the science here is just wrong, and the people directly involved in the work (or at least in publicizing it: http://emdrive.com/faq.html) seem to not even know the science well enough to recognize that it's wrong (or if you were inclined toward conspiracies, they could be knowingly obfuscating its flaws with technobabble). It's a case where it's all but certain that a big chunk of the enthusiastic public is getting set up for a fall. This goes beyond the challenges of your UR-FACT: something is clearly wrong in how this piece of science is being communicated to the public.

And at that point, if I as an expert see someone selling snake oil (regardless of whether they believe in it themselves), don't I have some sort of obligation to warn people not to buy into their so-appealing patter? The human cost here is clearly far less than the "vaccines cause autism" scam turned out to be, but they feel fundamentally similar to me. (As do the "bomb detectors" purchased at great cost by various government agencies in Iraq, as do the "magnetized water" devices that get sold to insufficiently skeptical farmers, as do...) Again, maybe you're right and the cost in this case is a drop in the bucket of legitimate research, but isn't one big purpose for society in training and supporting experts to ensure that there's someone around who can police this sort of thing? (And, more philosophically, isn't a big part of society's purpose in supporting experts the hope that we'll help to uncover and disseminate fragments of Truth, whatever that may mean?)

Clearly, we (and especially I, it seems) do a pretty poor job of it, if so, as illustrated today by the perennial popularity of this story. I really don't know how I or we can do better (clearly today's angle hasn't gone over as well as the last one did). Maybe it's all some sort of status-driven signalling, as you suggest, and my chatter about the public good is just so much self-deception. There may be value to the recommendation that you've made on that basis. But I'm not sure that I could live my life (or any life) with that framework as my premise.