I realized sheepishly this morning why the emails didn't go through: because the placement code never actually executed. Or rather, it did, but it turned into a no-op because the post was already ranking higher, due to user upvotes, than the rank (#10) where the code would have placed it. I forgot that I'd added that check.
So my complaint turned out to be nonsense, partly because it was 3am or whatever, and partly because "wtf? swear, profanity, curse...oh wait" is my normal debugging process. Just not usually in public.