Wikipedia takes a lot of flak for its processes and politics. I'll skip the debate on which of these complaints have merit, because what I want to discuss is some of the specific policies that the community has adopted. Like everything else, the policy pages were developed over time by the crowd, and I think they well reflect some essential guidelines necessary when a wide group of people must reach agreements (as is the case wherever humans share a space, whether that entails writing in the same wiki article or living in the same nation). In article histories and discussion pages, the policies are frequently referenced by well-known abbreviations, and I have found myself wishing I could do the same in non-Wikipedia contexts.
Other stuff exists (WP:OSE) - Sometimes articles get deleted. These decisions are often preceded by lengthy controversy, and some argue by citing precedent. "There's an article on x, and that's just as famous as this." This one comes to mind when people use US military spending to justify other federal expenditures. "We spend x dollars on a useless war, and universal healthcare costs less than that." The argument lacks validity because it hinges on the correctness of some "other stuff" which may have been wrong in the first place.
Verifiability, not truth (WP:V) - Although the concept may seem obvious, it can be difficult to accept that even if your knowledge is true, it has no place in the encyclopedia unless you can provide reputable references. Wikipedia ackowledges that capital-T "Truth" is beyond its grasp, because each article's content must be agreed upon by a bunch of opinionated people from the Internet. Instead, information is judged solely on whether it is backed up by reliable sources. I was reminded of this policy when a professor dismissed hidden variable theories of quantum mechanics as irrelevant even if they might be accurate. He described the purpose of science as "finding efficient models", claiming that laymen are wrong to take scientific results as truths. In any arena, we operate with some contextual redefinition of truth which represents but does not entirely concur with reality.
Civility (WP:CIV) - This policy is not wildly insightful, but I think it's worth a mention because I appreciate the way Wikipedia deals with negativity. It's a hell of a challenge - one that is not always met - but it's cool to see people choosing civil behavior because it is more effective than aggression.