Here's a particularly low-quality question I've just spotted:
I've flagged it, but it might be worth using this as an example to train the quality filter with.
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Congratulations, you have found one of the questions that the quality filter allowed through so that people could judge it in the review queue and get that little bit closer to their next silver or gold badge.
If the quality filter caught everything then there would be no meaning to life - edit and review privilege levels would no longer be required, therefore reputation would no longer be required. Any reputation currently in circulation would become worthless, causing a Global Financial Crises on the reputation currency exchange where due to hyper inflation 100K of reputation is now worth less than one Zimbabwean dollar. Shortly after that the life force, the Qi, that pumps through Stack Overflow would diminish to nothing (the guys over at Math.SE could probably do you up a quick formula to tell you exactly how long that would take, and the guys at Physics.SE will tell you how long it will take if you were in a vacuum with the gravity of two Suns nearby, while the guys at MartialArts.SE will tell you how to regenerate the Qi (which will mess with the pointy heads on Physics because they totally can't grok that)). Once Stack Overflow stops, millions of geeks the world over will no longer have anything to live for and will be left wandering lost and alone in the wilderness, with nothing to guide them through their dark days. Remember that scene in Terminator where the light in T1's eye finally goes out? It will be like that.
TL;DR: the quality filter is the enabler of life. Try not to question it for it knows more than you. One of the things we learnt from Part III of The Matrix is that it is healthy to have small amounts of randomness or chaos or unknown in a system.
This, my dear comrades, was satirical. I'm also bitterly disappointed in the quality filter. We should ask the dev's to give it a jolly good shaking and scolding. It happens every time - once these features grow up and get released into the wild they never behave quite the same way they did in the lab.