I’d guess that asking why you were downvoted makes other people think about why you were downvoted, and hence think about voting you up or down, which both overrides the previous vote since people vote to move numbers towards where they think they should be and also changes the mix of voters.
It may also simply draw attention to the comment thread due to people seeing the “why downvoted?” comment appear in the recents comment list. The more people reading a comment, the more who may vote on it. Inexplicable downvotes tend to persist more in long comment threads, low on the page, on older posts.
I’d guess that asking why you were downvoted makes other people think about why you were downvoted, and hence think about voting you up or down, which both overrides the previous vote since people vote to move numbers towards where they think they should be and also changes the mix of voters.
It may also simply draw attention to the comment thread due to people seeing the “why downvoted?” comment appear in the recents comment list. The more people reading a comment, the more who may vote on it. Inexplicable downvotes tend to persist more in long comment threads, low on the page, on older posts.