Hacker News is biased so that the threshold for flagging is very low, in order to maximize the effective separation of signal from noise as much as possible (for as broad a definition of "noise" as possible.) If I had to guess it's probably 3, or it's tied to user karma (flags from higher karma accounts count more.)
And certain topics are likely to be flagged by multiple people, this can be assumed based on the topics that people complain aren't "HN worthy." Anything that can be considered politics, for instance, is probably going to get flagged because of the number of people who don't believe political stories of any kind have a place here.
And certain topics are likely to be flagged by multiple people, this can be assumed based on the topics that people complain aren't "HN worthy." Anything that can be considered politics, for instance, is probably going to get flagged because of the number of people who don't believe political stories of any kind have a place here.