While I've always transferred the bulk of my np around via HTS TPs, I've recently started relying on overpriced daily items in shops.
Thanks to the semi-random mass inflations that Coincidence quests cause, I suspect that mass-buying of overpriced "junk" items no longer serves as any sort of reliable flag any longer. Otherwise, they'd have to flag just about every restocker.
I'll post back if anything bad happens