Q:

Why does math.stackexchange use single transferable vote?

Isn't the Schulze method superior to single transferable vote?  It takes preferences, and it's Condorcet (i.e., if everyone prefers A to B for all B in hypothetical two person elections, then A wins.)  STV is not Condorcet.
I can understand national elections using STV since the Schulze method would be impossible to explain to an average electorate, but math.stackexchange is made of mathematicians.  Why do we use STV?

A:

Within STV you have to specify the variant. We use "Meek".
http://en.wikipedia.org/wiki/Meek%27s_method#Meek.27s_method

If you are electing multiple people and simplicity is not important, then we recommend Meek STV. Most people agree that Meek STV is the best variant of STV, but it can only be implemented with a computer program.

http://www.openstv.org/faq

