For example, your Service should execute the unfavorite and delete actions by removing all relevant messaging and Twitter Content, not by publicly displaying to other end users that the Tweet was unfavorited or deleted.

Edit: I know there are some exceptions. For example, the Library of Congress (in the US) is building a permanent archive of all tweets older than 6 months. They have said that if you wait longer than that to delete your tweet, they won't remove it from the archive. I wonder if Twitter would consider a 24-hour rule for official political accounts? If the tweet is left up for 24 hours, then even if it's deleted from the twitter stream, you don't have to delete it from your archive.

Respect the privacy and sharing settings of Twitter Content. Do not share, or encourage or facilitate the sharing of protected Twitter Content. Promptly change your treatment of Twitter Content (for example, deletions, modifications, and sharing options) as changes are reported through the Twitter API.