I think you should charge people $1.00 per year to join A2K. That would immediately filter out the "drive-by shooters".
Unfortunately that would probably just filter everyone
(new) out, leaving the site to decay through atrophy.
There are better ways to solve the rather simple problem of people wanting to talk about different things on the same site. Instead of trying to make the entire site's stream of thought be monolithic it should, instead, merely better support diverse streams of thought.
So the model of a single firehose of "new posts" doesn't really work well and it should better allow users to pick what should be in it or not.
Every since the site began there has been the problem of some content not being desirable to others (word games, politics, rap battles, water softeners...) and the solution isn't to try to block it from the entire site but to have the site better support its scale.
Things like decryptonite (or any niche that not everyone is interested in) should be a microcosm that you don't notice. The problem is simply that we can't expect everyone on the site to be interested in all the topics and putting them all together in a single "new posts" firehose does not scale well to diverse topics.