Part of the problem might be that some people post direct from the site's home page, rather than by going to a section (or sub-section) first. If you type a question into the box on the home page, you're then asked to 'Select a category', where the options listed DON'T include 'Politics' (or any other subcategory).
I've long argued that the facility for posting questions directly from the home page should be removed. (Apart from anything else, it means that people can post in a section without ever seeing the guidance on posting there that the Ed has provided when going to the correct category first. It also means that people don't notice 'sticky' threads). In every other forum I use, one has to choose which section to post in, and go to it, before submitting a post. A similar system would be beneficial here too, I feel.