What licensing concerns are there for using content from Stack Exchange in an academic paper?
Making a reference to CC Attribution-ShareAlike content is always okay. In fact, referring to any work is okay, regardless of the copyright status. Only content is copyrighted, not bibliographic elements (including author names and title). For example, the U.S. Copyright Office says:


  Copyright does not protect names, titles, slogans, or short phrases.




Quoting is a more complex matter. It depends on copyright laws, and thus your country. In most cases, if the material is quoted raw and the quote is kept short, most academic use should fall under the doctrine of fair use. By contrast, read also the article on derivative work to get an idea of these two extreme cases.

This is mostly a theoretical question, however: the scope of fair use is grey are in US Copyright Law, and provided you do it for academic purposes and in a good faith, you won't get into trouble.

Finally: if you really want to quote in a bulletproof way, either (a) consult with a lawyer or (b) ask the copyright holder for a waiver to relicense his content to you.