I wonder if we could integrate ElasticSearch in existing forums, so when members try to post new threads, there could be a screen underneath that could show or suggest similar threads that may already be created.
I could imagine something like this scenario...
I click "Start New Topic" under The Lounge Forum.
I start typing "Porn Actor" under the Title Box
Before I even click on "Submit Topic" there'd be a box below the Title Box that could say, "Similar Threads" or "Is This Already Being Discussed?" and it would start suggesting similar threads within that forum, and maybe sorted by relevance or popularity.
If it's a new topic or the OP decides to create a duplicate topic anyway (or if there is also a way to show if the poster can no longer reply on an existing topic in the suggestion box), the OP can still click "Submit Topic."