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?