I had the same problem. However, I don't think there's a problem with xdg-open. I don't think that xdg-open does any translation of %c or %i (see the source). The translation seems to be done by mimeopen.
I installed desktop-file-utils, and did update-desktop-database. It seems fine now, GI -- Little Johnny was a scientist. Little Johnny is no more. For what he thought was H2O was H2SO4. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
