Looking at Stack Overflow activity graphs, I noticed a

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Looking at Stack Overflow activity graphs, I noticed a strange drop in anonymous feedback. This is what happens when people who don't have enough reputation on the site use the up- and down-arrows on posts. Then I remembered: the 1-rep voting experiment. From April 3-5, 2024, these were turned into real votes. Then the experiment was turned off and anonymous feedback was back.

What I don't understand, however, it the gap in data from 2024-05-17 to 2024-08-30. I could see some error right after the experiment ended or a decision to stop recording this data. But neither of those options apply to the data I'm seeing.

https://meta.stackoverflow.com/questions/429739/pausing-the-1-rep-voting-experiment-on-stack-overflow-reflecting-on-the-feedbac

Anonymous feedback on Stack Overflow
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@jericson There was a bug that prevented recording of that data. It was introduced on May 17 and fixed on August 23. (Those are the commit dates, I didn't check deploy dates.)

That matches up with your graph.