Thanks for asking! I gotta say that every time that post pops up, it makes me a little sad for what Stack Overflow has become. I count 33 things that SO is not which amounts to at least that many behaviors that
lusers users have discovered that are to be discouraged. No doubt the list will grow.
It's also a little discongruous to have a list that includes both:
Stack Overflow is not paying people to answer your questions
which seems like a very natural assumption to make, and:
Stack Overflow is not Your Free Promotional Site™
which seems like a more obvious form of abuse.
I've never seen the question being used as "just-in-time documentation", but I can imagine being horrified by getting a link the the "people aren't getting paid" answer and seeing the rest of the menagerie that surrounds it. The subtle message is, "The site is powered by volunteers, you spammer!" Which leads me to the first suggestion:
Split it into 33+ questions with one canonical answer
This would go a long way to solving my objection (which is admittedly not that big a deal) and, I'm guessing, make the whole thing more approachable to someone who's crossed a specific line. Instead of being confronted with "bad behavior #21", you could point them to the specific misconception they have about the site.
It also will allow individual responses to have their own tone. I love the answer to:
Stack Overflow is not attacking you personally
but it takes on a darker tone when put next to:
Stack Overflow is not going to read all that
or other, more snarky, answers. When it comes to sarcasm, these's a race-to-the-bottom problem. On it's own, the first answer sounds upfront and honest. But when you start to suspect the answers ought not to be read completely straight, you feel like the victim of a verbal practical joke or something.
My second suggestion is:
Assume the best
I suppose that the vast majority of people who abuse the system need a slap on the wrist and a stern dressing-down. It's useful to have a bit of text handy for just that purpose. But I really think it works best to assume the best in others. I know it can be cathartic to throw a little bile back at a particularly hateful user, but that's not a good idea. Rise above.
The funny thing is that I'm convince the really terrible people won't even notice the tone. There's probably some psychology out there to back me up, but my intuition is that being abusive makes people ignore blowback in general. If so, a sarcastic tone only serves to frustrate the users most likely to learn form their mistakes.