Well here's another idea (with credit to my son): on the page listing all the threads, there are at present three columns: Thread Name, Number of Messages, and Last Message Date. How about simply adding a fourth column for Message Type, with a simple code system of one, two, or three letters, with an explanation at the top of the page - e.g. L or Lyr=lyric request; A or Art=artist information request; T or Tch=technical discussion about the website; O or Oth=other topics; or some such system. On the "create a new thread" page, there could be a simple check box system, to choose the correct category.

Then all the threads would still show in order, but searching by category would be easier. (especially as the size of the archive continues to grow).