There is a lot of discussion around meta about how to raise a helpful flag and flags getting declined, but I wonder:
Who raised the largest number of helpful flags on Stack Overflow and Meta?
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On here, the current leader would appear to be PeterJ with 3760 helpful flags. He even has more than the Smoke Detector spam bot. Peter is the only person with more than 3000 helpful flags so he's some way out in front.
To determine this, I simply went through the profiles of everyone who has the marshal badge.
Stack Overflow has 2.9K marshals so it would be rather more tedious to go through all their profiles. There's at least one person with tens of thousands of flags there because they've written a bot that comment flags on their behalf so they (or some other bot writer) are likely to be the winner there.
On Stack Overflow's Meta, there are 4 Marshals, so the winner is honk with 859 helpful flags.
The number of helpful flags used to be something that was kept secret, that changed when profiles were rewritten and the information was accidentally leaked. When someone pointed that out, they decided that it simply wasn't something that needed to be secret, so we can now see it on everyone's profiles, but as far as I know it's only there, so you'd need to scrape all profiles with Marshal on a site for any other site. Fortunately, they are all smaller than Stack Overflow.
Here's a list with all users with at least 500 helpful flags on Meta Stack Exchange as of 2020-12-14. To update this list, follow the instructions here, and please do not bump this post too often. Flags are important but not that important, and it's not a competition.