Episodes are now fully versioned (like wiki pages). Each page has a [history] link at the top that will give you the full change history and give you the opportunity to see the changes and revert to older versions.
Obviously, it would be desirable to have this for series information as well. That's a bit more involved, however, and will have to wait.
I also fixed a long standing bug in the wiki-diffs where it wasn't properly decoding UTF8 when displaying previous versions.