AskPG: Where'd my downvote arrow go ?

I've been a participant in the HN community for a couple of years now, and I noticed a few months ago that I no longer had a "downvote" arrow available to me on submissions and comments.

Whilst this is not the end of the world (as I generally prefer to upvote anyway), it would be nice to know whether this is a deliberate site policy (based on some kind of criteria), or a bug ?