Flags are issued by regular users like us though. What do you expect a moderator to do, except maybe manually intervene to "un dead" something if it seems like a case of overly biased flagging? That's assuming mods have the ability to do that (I've always assumed that they do).
People do get their flagging powers revoked for misuse. There was a time when I went on an overly aggressive flagging spree and my flags no longer had any effect. Months later I sent an email to hn@ycombinator.com to pledge more judicious use of flagging and to request the restoration of that power. I got it back then.
Since it's such a powerful action, it would be nice if flaggers had to at least justify the flag. Is it breaking a site rule? Is it spam? Is it not the original source? Does it actually violate the rules, or are you just using "Flag" as a mega-downvote for articles you don't personally like?
Yeah, that's the 'receipts for everything' idea and if you think it through, you'll realize it's at a minimum impractical and more likely just an outright bad idea. Where are these 'reasons' going to go? Who is going to read them or act on them? It sort of wants to stick it to those bad flaggers and misinformed downvoters or whatever but think about it applied to you. Do you not recoil at being asked by some random web app to justify your actions? Like, we're ostensibly here for conversation not to fill out TPS report cover sheets.
This is 'drink verification can' but for messageboards.
A lot of HN mechanism makes more sense if you can accept the idea that the goal is to promote good threads, and not, as so many people believe, to promote one set of opinions over another. Requiring justification for flags would immediately crud up threads with meta-debates.
A hard thing for people to accept, something that I think is an unstated part of the HN ethos but nevertheless real, is that it's almost always better to have no thread at all than a shitty one. Important topics will inevitably get an airing in one thread or another.
Flagging content should be a privilege that comes at a certain level of trust, and the privilege should be revoked by moderators for people that use flags to further an agenda.
Trust in forum users can be measured by various metrics - The Discourse forum software is a good example of how to do this: https://blog.discourse.org/2018/06/understanding-discourse-t...