> Non-commenting Hacker News readers are observable

So: a) you can observe/measure the size/source of non-commenting HN readers from various proxies b) you can make claims about the intellectual status or influence of users not logged in to HN as an outsider

It's obvious that a and b are orthogonal.

Truth. When I cross-post something on my blog that gains traction on HN, a huge spike from HN dominating my traffic origins appears in my Blogger stats.