Comment 1 for bug 137408

Well, as for point #1, it already annoys subscribers to the original, who get broadcast messages in any of the duplicates. I agree with your consideration for #2, though I think incorrect dupes are actually not that frequent to warrant such special handling.

You didn't propose a #4, which is unassigning and unmilestoning when duplicating (adding a comment if you would like to store the history of who the assignee was), and then hiding the whole table. I underline my strong opinion that the assignee of a dupe is not very important at all.