I ran into a user that has a swath of poorly thought out, poorly written, not relevant, and often just plain wrong answers (it appears this person has a very limited understanding of information security and chooses to answer many advanced questions). I went through all of their answers and gave a downvote on every one that fits into these categories (about 3/4 of their answers).
I came back several hours later to find all of my -1 for downovotes turned into +1 (in my achievements feed), and my votes appear now to have never been cast.
What is the reason for this?