People do get their flagging powers revoked for excessive flagging. It happened to me a while ago. Most people who lose flagging powers won't notice it because the UI doesn't change and there is no direct indication that your flags are being ignored. I eventually emailed the mods to pledge more judicious use of flags and ask for my flagging rights to be restored, which was enough to get them back.

And mods do step in, but the mechanism for drawing their attention, as I've noted, and as the HN Guidelines note (<https://news.ycombinator.com/newsguidelines.html>), is email. Not long HN threads about abysmal moderation.