Very similar to @Gnome's earlier question. The markdown for automagically-inserted duplicate links breaks if the duplicate contains a URL in the title.
In this case, markdown splits the URL into its own link, and text earlier in the title is given the correct link to the duplicate question. The URLs work, but it looks wonky -- the question link doesn't span the entire question title, and users aren't expecting multiple links there.
How does http://to./ work?
[How does http://to./ work?](http://superuser.com/questions/78408/how-does-http-to-work)