And even if people voted in the same way for anonymous monk posts as for others, the $NORM would still drop. Anonymous monks don't vote.

Of course, it could also mean that more and more people realise that XP is a pointless numbers game, not unlike the lottery (except that there's no price money), and no longer bother to vote. Or that the novelty of voting wears off over time - it no longer produces the thrill.

Or it could mean there's an increase of the number of posts per user (or rather, per vote cast). It's still possible for $NORM to drop even if no downvotes are cast at all. And even if every one logging in on a day casts all of their votes.