If you see a post that ought to have been moderated but hasn't been, the likeliest explanation is that we didn't see it. We don't come close to reading everything on HN; there's far too much.
You can help by flagging it or emailing us at hn@ycombinator.com.
I'm saying I don't think this comment you've flagged yourself "ought to have been moderated." Louis Rothman is a public figure. There doesn't seem to be any rule against attacking public figures
... or is there? If so, when and how does it kick in?
Also, just call them "rules." Calling them "guidelines" implies they can be broken occasionally if there's a good reason. It's misleading.
The GP comment (https://news.ycombinator.com/item?id=40242447) was flagged by users—lots of them, and rightly. It's a clear example of what we don't want on this site: personal attack, name-calling and snark, with zero interesting information. It doesn't matter whether the target is a public figure, because the issue is the poor quality of the comment itself.
You're right that they're "guidelines" not "rules" because there's a certain amount of slack. But in the current case, the comment went way beyond the slack.
