In the way I have set up
WordPress.org, it makes use of a caching daemon named ‘Memcached‘, that runs on my server and speeds up the fetching of specific, frequently-requested content. This is not to be confused with whatever cache is also speeding up your browser.
As part of a routine set of updates fed through my package manager this evening, this daemon also received an update, which required that it be restarted. As a result, the cache is now cleared, and the fetching of the favorite postings to the readers will be somewhat slow for the next few hours, or maybe even for a whole day.
I apologize if this inconveniences anybody.
Also, this behavior does not represent any sort of malfunction, either by the daemon, nor in the update process. All the updates seemed to go through just fine.