Other users of the road do most of the enforcement. The police often get involved only at the behest of another user or if certain levels of misconduct are breached. It sounds like this transparency allows other citizens to do the low-level enforcement: organizing against an unwanted company buying that attempting to acquire more ownership your town might be analogous to honking, tailgating, etc.
There are several points. One is to signal to the community that it's not ok to post like this. Most people don't want to get banned and do genuinely want to use the site as intended. Leaving a public trail of moderation comments and actions helps regulate community behavior, even if it doesn't have that effect on you.
Another is that I prefer to (try to) persuade users that it's in their interest not to abuse HN. HN is only interesting because there is a somewhat* higher quality of discussion and content here. When you post aggressively, violate the site guidelines, and so on, you're damaging the ecosystem and contributing to destroying HN as an interesting place. That is not in your interest.
I assume that you wouldn't drop a lit match in a dry forest, or dump engine oil in a mountain lake, or throw trash in a park that you enjoy. Why do the equivalent here?
(* I don't want to overstate that—a lot of posts also suck. But it's all relative, and there aren't many places on the internet to have the sort of discussion that, at its best, goes on here.)