Codeigniter development (v3.0)

[eluser]CroNiX[/eluser]
Why would a referring site use an underscore if the link on the site uses a dash? I can see that being a problem if a site originally used underscores in links and search engines/referring sites cataloged the link that way and then the site later converted to dashes. But if the links on the original site had dashes from the get-go, where would a referring site get underscores from?

If a site did convert their url scheme at some point, shouldn't they be responsible for creating htaccess rewrite rules for dealing with that before the code hits CI?