It's one thing to have a poor-quality code base. It's another thing to be proud of it, to the extent that you boast about your highly questionable decision-making in a blog post. I don't envy anyone who joins this company and has to deal with it.
I'm with you. I read this and I think, "ok, well, it's StackOverflow, and they're obviously a bunch of really smart people... but they're still doing it wrong". I've been doing Java for 20 years now, almost since there was Java. I've observed that most Java developers migrate toward "everything is static (i.e. global)". In fact, the abomination that is the Spring "framework" more or less requires it. I don't believe they do it for performance reasons, I believe they do it because you don't have to think much (up front) that way, and you can just kick the can down the road.
SO has been wildly successful, the site is consistently fast and reliable, and it doesn't seem like their decisions have significantly held them back during development. None of this sounds "poor-quality" to me.
