The problems you want to address are real. I also have seen the drift in HN over the years, as zealots start to outnumber (or at least out-post) those who will actually think.
But I suspect that tools aren't good enough to reliably work. (Do you want this post, say, marked as FUD because of a negative take on HN posters?)
The best answer I have is to parallelize dang. Downvote it when you see it, and don't feed the trolls (that just gives them a chance to make another comment). If it's particularly bad, downvote and flag. (I'm not sure what the threshold is to kill a comment. It's more than one flag, but it's not that many. I suspect it's in the low single digits. If very many people see the problem, and will bother to flag it, bad comments will quickly die.)
But there are at least two problems with my solution. First, it hasn't been working so far, or at least it hasn't been working well enough. It working better requires a change in behavior (and more effort) from the established users, which is kind of a tough ask. Second, this is something that could be turned against us if a block of zealots decided to mass-downvote and mass-flag things. I mean, we can vouch for dead comments, but that's also work...