Anyway, not to rock the boat, but I've recently been the target of such downvoting without comments. The three recent ones that I can remember were on questions that I answered that were followed by another person posting a similar answer. What's funny is, I received votes down (without comments) on a correct answer that was offered first. I suspect that the people responsible for those votes either did not understand my answer (or how it was the same as the other answer), or they decided to vote that way out of spite.
I offer this as anecdotal evidence that there should be reasons given for voting down a post. I think it's pretty irritating to have no explanation, and worse, it seems to encourage bad voting practices.
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