To copy claims between discussion, use the same technique as in Moving/Copying a Claim. Add the claim to your clipboard, go to the discussion you would like to copy it to, and drag it to drop it into place.
Unlike the hyperlink that appears when linking an entire discussion (see: Linking a Discussion in Another Discussion), the copied claim will look like any other claim.
If doing this, keep in mind that it will also copy all claims beneath the copied claim. It is advisable to review child claims first, to ensure they are related to the new location.
Once a claim has been copied into a new topic, edits to that claim will not affect the original location, unlike when a claim is copied to another location within a topic. You can therefore make whatever edits, deletions or restructures are necessary to fit the branch to its new location.