When browsing around old questions, I came across this one. It was marked as a duplicate of this one, which was in turn marked as a duplicate of this one. This is the first time I've come across something like this. I was just wondering - why? Why would a question be marked as a duplicate of a duplicate?. Shouldn't the first two questions both be marked as a duplicate of the third?
Technically, yes, they both should be marked as a duplicate of the original. But in the end, it doesn't matter too much.
Users can quickly and easily follow the trail back, and the trail is only short. The user will still be able to see the original question, and see why the closed question is a duplicate.
I imagine this occurred due to key words. When voting to close as a duplicate, a list of 'similar questions' will appear, and these questions are ranked on key words - i.e. how many words match another question. If a question has the same/similar body to a closed question, that closed question will appear top of the list.
As well as this, when others vote to close, the question the initial closer voted was the original will be at the top, and other close voters probably simply clicked that question which is why it was marked a duplicate of a duplicate.
Hope that helps!
Actually, the trail may seem unnecessary, but it may also be a good thing.
By linking duplicate after duplicate, users who are trying to find an answer can navigate to the duplicate that best suits their needs. If all the duplicates where linked to only one post, than users won't have many options.
Every duplicate hold a small unique piece, that put together, can be a lot!