Interesting question Burke, Hear is my guess as to what happens, other threads seem to bear this out.

The thread prefix is added to the thread title to make the name of the thread. There are 2 ways that a post can be made to a thread: either as the first post in the thread where it appears that the subject prefix (if any) is not added or as a follow up post where it appears that the thread title, which has used the prefix is used.

Speaking as a JoeClone, the indiviual subject headings can be edited but it is unlikely that they would be as it the text of the message that usually causes problems and these are separate fields.

Although a JoeClone could alter a subject heading, the task is fixing broken threads - i.e HTML errors and/or marking lyrics as being harvested.

Jon