Considering the upvote count even the hot rising posts on front page have. I would assume the flag threshold to be quite small. I don't know if each flag vote counts the same or does it depend on karma/account age, but at least from upvotes I would assume you would need less than 50 flags to pull even a hot story. So, paid influence ops should easily succeed in HN; whether they have even bothered with HN because of small audience size, that I don't know.
In most cases it is the politics aspect or the unfair coverage aspect that leads users to flag a story, like say on lab leaks; but this story being flagged so easily was interesting. It is about a tech platform intentionally/mistakenly censoring things we will count as free speech.