Duplicates are there mostly to tell us that a question was already asked and, in some cases, it also has an answer and to link to this question.
While this is great for main sites, on meta it's a bit trickier.
We know that on meta we:
- discuss various topics
- propose various features
- ask for support
- and report bugs.
We also know that on meta, voting is not working the same as on the main sites. Here, it represents that others agree and supports that (or not, in case of downvotes).
So, when we meet a duplicate on meta, it actually means that somebody else who didn't find the original post agrees and supports the same question and that whoever upvoted / downvoted the duplicated question, also agrees/disagrees with original post.
However, if I'm not totally wrong here, those votes are lost - we only know there's a duplicate when we visit the duplicate question. The original question doesn't show that in any way in the UI.
- We should show, in the original question, that the same thing was requested in other words;
- We should sum the total of upvotes/downvotes, in the original question, and display them in the UI broken down per each duplicated question
But why not sum the votes directly you ask? Why show them broken down per duplicated question?
Well... having full transparency as to how the voting occurred might be relevant when making the final decision (e.g. status-something), and might help others to agree/disagree by seeing other points of view that are considered duplicates, and how others perceived them.
Obviously the linkage and summing the total votes needs to be validated, so that if the same person upvotes all duplicates / upvotes one and downvotes the other, the total votes is still consistent and reliable.
To that end, I would simply show latest vote from a distinct person.