If you happen to have the same username exists in both local Confluence and LDAP and the LDAP username is in uppercase/initcap, accessing the people directory shows duplicate users. Please see the attached screen shot:

Here are the steps to reproduce the problem:

1. Create a local user named "alex fong" for example
2. Perform the LDAP integration (presume that there is an user named "Alex Fong" with initcap in LDAP)
3. Grant permission to the LDAP user
4. Login with "Alex Fong" credential
5. Clicking the Preferences link
6. Accessing the People directory

You should be able to see the duplicate entries. This problem is also happening if the username with uppercase/initcap are from LDAP and not exists in local Confluence.