This is an ongoing battle, the latest initiative has been to try encourage better behaviour.
I can see that the biggest offenders are new users, they make no attempt whatsoever to look for relevant topics and cut and paste a slab of (generated/processed) text into the composer and go straight to opening a topic.
In an attempt to influence that pattern, I built a custom theme component that for the new user trust level, checks the amount of time they have spent reading and if it is less than 5 minutes, locks the new-topic button, with an appropriate tool-tip explaining why. If the button is clicked it opens the community guidelines page. New users can still add comments to existing topics.
Hopefully this will have a positive effect, at least spammers will have to put a bit more effort in as well 
