There's a long tradition on HN of users flagging stories on highly politicized topics, because such discussions typically become ideological and uncivil, two qualities that we seek to avoid in discussion here. That's what happened to that AR-15 story: [flagged] means users flagged it.

We've learned that such flags are an important community signal and it's a bad idea to override them unless there's a clear reason to. I didn't see a clear reason, because (a) the article was deliberately provocative, (b) its timing was particularly provocative, to the point of trolling, and (c) the discussion (though not as bad as it could have been) was close to flames, and likely would have become a full-out war if we had intervened to turn off the flags. Flags are a pressure valve for the functioning of the site.

On HN, a situation like that is complicated and involves multiple factors other than intellectual curiosity, which indeed are stronger than intellectual curiosity and tend to drown it out. In your description of the article above you highlight only the intellectual aspect (clear description of a little-understood technology) and omit the problematic ones, but the latter nearly always overpower the former. By contrast, stories about contested 8th century papyri are clearly on-topic and not particularly likely to violate the values of the site (marginal religious skirmishes aside).

If you were particularly interested in the AR-15 story, I can understand the frustration of seeing others flag it. Most HN users have the same frustration, but we all have it about different things. Other people complained yesterday that the AR-15 story was (in their opinion) being featured on HN while the latest post about Jacob Appelbaum was (in their opinion) being suppressed. In fact it was the same factor—user flags—working the same way in both cases, and the application of HN's standards wasn't selective. It just seemed like it was, because we notice it more in any case we dislike.