When a question is closed as an exact duplicate, the behaviour is not ideal at all. For reference, here's an example question I'll use.
Firstly, the closed message which describes why it was closed ("exact duplicate") is shown very far away from the link to the question it duplicates, so users are forced to mentally process all the text on the question to find out where to go to contribute.
Secondly, the automatically-inserted duplicate block says "Possible Duplicate" (even though by closing the issue, the editor clearly feels it's more than a "possible" duplicate).
Thirdly, the answers to the question are orphaned from the active discussion. The only link back from the original question to any exact duplicates where an interested party could find additional answers is the "Linked" section in the sidebar near the (always wordy) related questions section, and the authors of answers aren't informed that the question was closed (to theoretically go and add the same answer to the original question).
I'm sure it's a platform issue more than a UX.SE-specific one (but given I feel it's a UX issue with the site, perhaps this is an appropriate place to discuss the possible solutions).