However, I hang around here sometimes to check on updates to some of the extensions I use in my personal wiki, which I've installed on my computer mostly so I can play around with a wiki on which I control everything ("[I] will control the horizontal; [I] will control the vertical," so to speak). So I leave messages here and there, and sometimes attempt to debug problems. Someday, I plan to get more familiar with MediaWiki's APIs and write my own extensions, but for now, I just patrol the ones here.
I've also started participating at the MediaWiki support desk, answering questions from other wiki admins. As I learn more about MediaWiki from my own experimentations, I hope to be able to start answering more and more complicated queries.