<i>I've written many times [...] so I was caught by surprise</i><p>Reading that, it occurred to me that one of the gotchas here is the statelessness of the web. "Statelessness" isn't quite what I mean. "Contextlessness" might be better. URLs are pointers that jump directly to content that mostly gets consumed atomically, without reference to anything else the author has said/done. Of course if readers want context they have ample opportunity to explore: look at what else is on the site, google the sources and so on. But most won't. (I often do, but I didn't this time.) I wonder if one way to mitigate this is to make content more self-describing.