The mechanism for looking up links when deleting a topic could result in broken links remaining.

The implementation stores "tid&fid" in the moved_to field of the topic link and then when deleting a topic, the topics are searched for any links that have "tid&fid" in them where the fid is the forum_id for the forum containing the real topic.

Problem is that the real topic could have been moved twice or more leaving multiple links. The implementation will only find the last link.

You probably should use LIKE to find all the links for the real topic as if you allow deleting a topic leaving a dead link, anyone that clicks on the old link will get a "broken" error message.

This is not a bug in IPB but is more of a feature suggestion.