When reading some old wiki page revision, the crumbs will only go up to the page address. It would be good for them to follow the path for the version shown. An example:

You are here: Home > Crumbs for wiki page revisions > Revision 2

This suggestion should make it more visible that what you are reading is an old version, not the current page. It is somehow related to the suggestion WikiPageTitleIncludesRevision.