Add merge option, instead of or in addition to linking
Linking results in hidden entries. Later the user may not realize that a contact has linked entries (unless they happen to check). Rather than linking the contacts, especially after importing, add a Merge button that pre-selects the duplicate entries, presents the list, and lets the user merge the duplicates. Then there is just one entry per contact.
Absolutely merge contacts instead of Linking!! Who on earth needs 4 contact entries for the same person?