There should be a little textbox like the tags textbox which allows users to keep a list of duplicate questions, e.g.:
3423 23423 2232
This would be cleaning than posting the links in comments and since you have the question numbers, you could add a button which allows the user to "show all answers to all related questions". Might even be useful to consolidate the topics into one for search engine ranking?
And it would allow people to re-ask the same question from time to time, since the answer to e.g. "what is the best x" in Dec 2008 is not the same as "what is the best x" in Jun 2009.