Especially on the Atlassian JIRA (=this) system, issues are frequently created and later found duplicates of others. (Happed so e.g. with CONF-6827 for me)

If a issue is resolved as duplicate, it could make sense to copy/merge the votes and watches of the resolved issue into the one which is "left open".
Otherwise, the votes are lost (at least until all the voters also vote for the "left open"-issue) and the watches are also more or less useless because no further changes will occur on the resolved issue.

Therefore I think it makes sense to merge/copy votes and watches.

The are possibly circumstances when it does not makes sense, so I propose to add "Merge Votes and Watches" as a option which is enabled by default but could be untagged/disabled.
From my perspective, the option should apply only if a issue is resolved as "duplicate".

Martin