Okay, this might be an insight.
When I visited PerlMonks Discussion just a moment ago, the first thread listed was “My Thread Disappeared.” But when I logged in, my (of course, seriously-downvoted) thread appeared first.
So, is there, say, a “sundialsvc4 filter?” It would not surprise me, of course, since I seem to be someone who can collect fifty down-votes for reporting an apparent problem with a web-site to the people who are supposed to be responsible for maintaining it.
Well, no, because the “stale content” that I saw a few days ago did not concern my posts, nor my replies. Nevertheless, it does suggest to me that what I am seeing is some kind of difference between being logged-in as oneself vs. being logged-in as Anonymous Monk, as opposed to a pure cache-stale problem.
Also, when preparing this post, my session briefly disappeared. Again.