1)Joe, do you want to be specifically alerted (by personal message) to superfluous threads so you can nip them in the bud? Example. There is a thread Ard Tí Chuain / Quiet Land of Erin (by the way the Irish name should be corrected to Airdí Chuan or Aird a' Chuan). Someone else started a thread seeking for the Quiet Land of Erin. Although, you directed them to the older thread, a couple of other people jumped in to discuss the origins of the thread. So now there is some useful information in that thread ... it could be diverted to the earlier thread, but since some of the info was already there, it would make PJ look very foolish indeed in suggesting that the song originated as a butter advertisement.
In recent weeks, a third Quiet Land of Erin thread started. Someone replied with a link to earlier threads. But the thread originator thought she was being helpful when she subsequently pasted lyrics from the earlier thread in to the new thread! I scolded her, not for thread proliferation but because she quoted some comments I made and did not make it clear that the comments were not her own.
As there is no new information in that thread, I think it could be safely deleted before someone does add new info to it. But what about the problem with searches -- if you change a thread title or if you delete a thread without refreshing the old one (and even if you refresh, but the older thread has a different name), you frustrate anyone trying to reach the thread by the "refresh" box. If you delete a person's irrelevant entry -we discussed deleting 'refresh' messages - that person might unsuccessfully look for the thread by searching a list of their past messages. Have you worked out any solution to the search engine complications?

Another recent superfluous thread is "Ag Críost an Síol", which the originator uses to guide people to another thread titled "Ag Criost an Siol" ... maybe you should nip it in the bud before messages are added to it.

Although I suggested to that person that the thing to do is add a message in the earlier thread with "Ag Críost an Síol" as the subject heading for the message rather than the thread, I have found that putting "Making Babies By Steam" as subject message in the "Daniel O'Connell & His Steam Engine" thread hasn't made any difference in the non-linkage from the DT "Making Babies By Steam" to the thread that contains the most information about the song. So I did start a "DT Study Thread". My limited viewing of these study threads has not convinced me that they aren't more unnecessary work and thread proliferation(?).