But I just came across this review item, and was unable to flag it as spam.
edit: Since I posted this, the item has been removed (deleted) here is a screenshot:
And the sooner it gets there, the better. It should always be possible to flag a post as spam — when reading it, from a review queue, preferably even from the post feed in a chat room.
But at the very least there should be an option to flag a post as spam from each and every review queue.