The ability of local agencies to just post to your feed has been a feature of Nextdoor for years. They can also close their posts to discussion, which is pretty irritating.
It might go without saying that I'm slightly even less impressed with Next Door than when I wrote the original comment, but it does make me think: is this product bad because of the people it attracts? Is that its fault, i.e. could it be targeted better or formatted better (think Stack Overflow vs web forums)? How could the problem be solved in a less obnoxious way?