I don't think this situation can really be described as a trick.

The way I see it, the main services publishers provide are distribution, marketing, and to a lesser extent editing. Self-publish or go with a vanity publisher, and you're going to have a harder time getting into bookstores or other content distributors, because you haven't gone through their filters but also because you're not playing the usual game. But that just means you need to establish the book's worth yourself. The typical reader won't be able to tell the difference, but in order to get your book to the typical reader, you need to jump through a lot of hoops that are more or less equivalent to what a publisher would be doing for you. And popularity of course is a vindication all its own (there have been successful self-published books, albeit not many).

Now, if the question was whether it's ethical to claim the status you'd get from being picked up by a major publisher ("I'm a published author!"), then I'd be right there with you. But I don't think that having a vanity-published book in the wild, or even pointing people to it, is equivalent to making that claim.

Your line of argument looks strange to me. Basically, you are saying that any writer MUST go through gatekeepers to reach his readers and if he bypasses the gatekeepers that's fraud and deceit upon the readers. I don't find this approach reasonable.

Sure, but that's just editing. Which is one of the basic services of a publisher; they have an interest in catching your mistakes and generally helping you not look stupid, because that sells, but that's not the same thing as being nontrivial evidence of intellectual credibility. Obvious bullshit and pseudoscience gets published all the time, because that sells.

"This describes the most important scientific and moral challenge of our times", and you had never heard of MIRI/FHI/CFAR/LW in any way whatsoever, what are the questions you're going to ask?

"Why do you think so?"

They'll almost definitely be credibility questions;

Not in my case.

you want to read a book that's been edited well and comes from some kind of well-known intellectual expert on the topic being discussed, preferably one from very credible institutions like academia and government.

Oh, certainly not. Government is pretty much the opposite of a "credible institution" and as to academia, it depends on the field.

Digital or not, the fact that an article or book has passed the filter of a reputable publisher provides useful evidence in estimating its quality.

Yep, the word for that is curating and it is a common and valuable activity. Art museums, for example, play a similar role. On the web brand-name blog collections (e.g. the Gawker stable) is also basically about the same thing -- in this particular case, though, I don't know if we're talking about quality... :-D