I just came across this question while reviewing questions with the mail.app tag:
https://apple.stackexchange.com/questions/5987/mail-app-import-from-entourage-failed (edit: this link now points to the same question as the link below)
I noticed it because another question with a very similar title was in the list a few rows away:
The first question has been merged into the second one. It would've saved me (an admittedly small quantity of) time and trouble if the title of the first question was marked with [Merged], [Closed], or something like that. Is this possible? Does merging happen often enough to make this a useful enhancement?