Hey @codinghorror, have you managed to replicate this?
The evening I wrote that post, I cleared everything from Zero Replies through 2 Replies (part way into 3 actually), and sure enough, they’re back in droves tonight.
ETA - There were roughly 55 unread in the 1 Reply category tonight, in spite of me regularly clearing that section for many repetitions now.
ETAA - And about 34 in the 2 Replies filter, including these ones several times for sure now: