One of the reasons I left this post up is to make it clear that there is a bug with posting (so the bug can be fixed more easily). Now I see the same thing happening with other posts, e.g. the one here
http://community.wolfram.com/groups/-/m/t/294368?p_p_auth=5sFXRgOc
by Neven Golenic, is affected by the same bug. (It appears to repeat the text of the post it is replying to.)
(The other reason was that since I only had access to an iPad at the moment, I couldn't fix it, and after the post has been up for a while I needed to add an explanation of why this happened.)