On 4 December, there were many downvotes without explanation. The user used the Recently Active feed to select the questions. Old questions that were bumped by the Community bot were downvoted without explanation. A search through the feed shows many examples of single downvotes without any substantiating comment. The following posts contain downvotes I consider dodgy:
The user was either being very critical, was in a bad mood, or doesn't understand that it is rude to downvote without giving feedback.