While going through Rakesh Joshi's reputation tab, i found that, he had lost 145 points on Nov11. It clearly looks like someone serially unupvoting his several posts. Here is a screenshot:
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Now, i know 1."What is meant by an un-upvote?" and 2. serial voting not allowed and they are auto-detected by system.
In this case, however, the unupvoting was not reversed.
Hence the question: Is serial unupvoting allowed and not detected by system?