I don't think JADE will have any trouble, as Java is inherently Unicode-aware.
But neither PHP nor MySQL inherently support Unicode, so it has to be written into the software... not a pleasant experience (phpBB3 reimplements many PHP string functions for Unicode... ugh).
Latin-1 works in a preview at least, but I don't know how these characters will show up in a post: ?
EDIT: Yup, it's definitely a filter of some kind on the DB, because I saw the characters in the preview. But vBulletin is proprietary, so I can't do some good old-fashioned source-diving to find the problem and see whether it looks fixable.