When you first walk into a suggestion thread, like this one, you have two options: Support or No Support. Until you hit one of these, you are 'neutral' on the subject of voting; you have abstained.

Once you hit one of them, however, you are condemned from abstinence. You now either Support it or you don't. You can no longer return to being 'neutral' on the subject of voting.
This really sucks if you change your mind about your vote and don't know how you feel about the suggestion at hand. You're locked in a binary system the second you vote.

We should be able to un-Support/un-No Support without having to switch the vote over to the other side.
Kind of like how you can un-like a YouTube video after liking it, and not outright leaving it a dislike.