On the contrary, the stated purpose of SO is to be the repository of programming related questions and answers - to the point that moderators routinely go in an

On the contrary, the stated purpose of SO is to be the repository of programming related questions and answers - to the point that moderators routinely go in and edit questions so that they are more clear. So, the goal isn't so much to help the one person who has the question at that moment in time, but the masses of people who will have that question in the future. With that goal in mind, then answering your own question is clearly in the spirit of the site.