i want to suggest the ff for easier moderating...
let say you search for certain topic, then you see on the results that a certain user posted
exactly the same question....
you want to merge all those same topic posted by the user.
its so tedious to merge topics that are not in same date because you have to browse it one by one.
i suggest to have a admin/moderation checkbox in the searching results page.
that way its easier to manage same users with duplicate topic.