Which looks like this
Perhaps not only me.
My other experience says if I click arrow Up that means I agree with the idea, support it and thus Upvote. If click once more I changed my mind and remove my vote.
If I click on arrow Down that means I disagree with the idea, better not to implement it and thus Downvote it. With such approach the idea could have negative number of votes, that means people don't like it to be implemented.
Here both arrows means the same, just Upvoting. Better to change the behaviour or, if TechComm team doesn't like to implement Downvoting for any reasons, change arrow down on something else which confuses the people less. Don't think that's a big job.