The pattern seems clear that these users are flagging the more sensational kinds of submissions that tend to lead to predictable discussions and flamewars. There's room for competing opinions about which of those are/aren't on-topic for HN, given the site guidelines; if you or anyone want to understand how the mods look at it, I recommend the explanations at the links below. But clearly the flagging behavior in this case was in good faith.
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...
Want to censor a thread on HN? Flag it with a few different users, or turn the thread into a shitshow so that the "flamewar" tools will be triggered, or moderators will be forced push the thread off the frontpage.