I'm not a big fan of the People Hub view in Outlook 2013's contacts. It's too cluttered, it's confusing. While you can edit contacts in the contact cards, it supports only the main contact fields. If you want to edit the contact photo and add (or open) attachments, you need to open the full contact.
Accusations that Outlook is too complicated are right on target when it comes to contacts. Many new users are confused by Contacts and Address Books. Outlook 2013 gives us more confusion with contacts and contact cards, and search results that include the auto-complete list.
Most people probably wouldn't notice, but it's clear from my Search People results because of the entries for messages associated with a moderated mailing list I own.
While it should be easy to identify auto-completes because they don't have friendly display names, they clutter the search results and can't be deleted from the results window. You need to remove it from the auto-complete list.
To remove non-existent contacts from Search People, you can delete one address at a time by starting a new message and typing the first letters of the address, then selecting the address and deleting it, either with the Delete key or by clicking the x beside the address. Close the message form when finished. You can clear all names from the list in File, Options, Mail. Look for the Send Messages section halfway down and click the Empty Auto-complete List button.
Tip: dock the People peek and search in it instead of using the Search people command. While it also includes entries on the auto-complete list, the window can be re-sized to display more entries and the search results will stick around until you clear the search.