I recently wrote an answer to a question here. I thought it was a really good question and since the topic is somewhat neglected on the Sacred Wiki, I thought (however blasphemous) to edit its entry. Besides being blasphemous:
Thx
Regarding legality: If you wrote that answer yourself, you are the copyright holder, you just decided to license the text for Stack Exchange under the CC-BY-SA license. But you are still free to license that text to others (e.g. Wikipedia) under different (or same) license too.
If someone else wrote the answer, there are two questions:
As mentioned above, all questions and answers on SE sites are licensed under CC-BY-SA, which means you can copy them as long you attribute the original author (e.g. by including a link) and don't restrict the use of the copy. Because Wikipedia also uses CC-BY-SA, this second condition is fulfilled.
So, the answer to question 1. is that if you include a link to the original, you are fine. (To include that link, you can use the CCBYSASource template).
Regarding question 2., read WP:COPYOTHERS. It explains that copying text from works “available under terms that are compatible with the CC-BY-SA license” is okay.
But another requirement for Wikipedia articles is one of verifiability, based on reliable sources. And a SE site is not a reliable source. What this means is that you can't use some answer as a source for a Wikipedia article, but you can include the text from an answer to an article, citing other sources (possibly ones that were already cited in the original answer).
Stack Exchange sites are considered to be Open Source sites in nature, so I don't believe this would be an issue. I'm not familiar with wikipedia's guidelines for source documentation, so I'm not sure they would consider our site to be a valid source, unless the answer you plan to use has further supporting documentation.
