Quite a few things don't include the last dash when linking URLs, e.g. on http://bugs.musicbrainz.org/ticket/5449#comment:10 and for me in Thunderbird. Instead the link is http://musicbrainz.org/cdstub/8eQ21jUNpf2l0SHhtab9Oo6gKYM which isn't valid.
As far as I'm aware, the last character is always a dash, so I think it would be nice if it would check whether the last character is missing, and if it is, add it automatically, instead of giving an error.
Another case: https://bugzilla.gnome.org/show_bug.cgi?id=651338