I've noticed that the summary contribution only follows the first tag submitted, regardless of ranking.

For example,

http://bitzi.com/lookup/Q553LEJYR36HNSJFHOX3UWVUP5TXAEP6

As you can see, I accidently wrote the wrong name for the album and, of course, it didn't show up properly. However, adding a new Audio Track tag (and ranking them properly) didn't change the overall setting.

Are there other features which seem like only a one-shot deal?

Basically it sounds like you want to modify or delete an old tag. I wrote about a similar problem with the Objective Description tags here:

http://bitzi.com/bboard/message?message_id=163554&forum_id=1667

Personally I think it'd be good to allow users to delete their own tags - at least have a 24 hour window after posting a tag to allow modifications. That wouldn't solve every problem, but I think it might help.