I don't think you can downvote front page articles, just comments. I seem to have hit the threshold to vote on individual posts, not sure if there is a higher threshold for articles.

Edit: and speaking of voting, since this got downvoted: I wasn't the person who downvoted you. I felt bad you got marked down and wanted to let you know since sometimes on HN people can be weird about "HN is not Reddit" :)

Posts use “flags” instead of downvotes. There’s no threshold to flag a post either.

I thought flags are for TOS violations, not pure disagreement. Or should I go back and flag all those who emacs users who besmirch Vi? ;)

You're correct. I can no longer edit my post, but I should have specified. There's no true "equivalent" of downvoting posts, just the flag system which downweights posts like downvotes do comments. After it reaches a threshold, the post becomes hidden.

It is supposed to be used strictly for posts that violate the guidelines (i.e. off-topic, reposts, incorrect titling, etc). If a user keeps flagging content inappropriately, action may be taken against the user instead.

thanks :)