If I insert a <!--more--> tag into a page I'm composing for my blog on wordpress.com it does nothing. The page renders without a jump in the middle. This is true of both the preview and the published page.
This used to work. I have a blog page from January of 2011 that contained a <!--more--> tag. It rendered correctly then, but I just went back and checked and it no longer renders correctly. I don't know when it broke.
The blog I need help with is cornercases.wordpress.com.