Bruce Schneier is more than a celebrity (though I did use him as an example because he's somewhat famous). He consults for Congress and is the author of multiple widely-used cryptographic algorithms (thinking here of Blow/twofish). He's an expert who also happens to be a celebrity, but I can still cite him as an expert without conflating the two.

>there are countless others equally or better qualified to speak out on topics of cryptographic theory whom you (and I) wouldn't recognize at all – but actual domain experts would.

If that's true, then I ought to be able to find talks these people have given, or papers they've written. Based on a quick google search, I concluded the author of this blog post appears to only write short, shallow blog posts.

Now, that might not be the case. You obviously dug a little deeper and found some more info. But that simply goes back to what I was saying in my previous comment. There is an increased burden of proof in a world where anyone can say anything on the internet. Nichols wrote a blog post claiming to be an expert? Okay, why is there no quick link to a summary of his qualifications in direct support of the article's central premise?

Who knows, maybe he's a public policy expert but a lousy writer.

Either way, my argument stands: On the internet, if you don't have name recognition and want to be taken seriously you have to demonstrate your expertise, because any layperson can quote a wiki article. It takes more than simply saying "I am an expert".