In your LDAP setup, you probably synced the LDAP user ID to the user_login and user_nicename DB fields in the wp_users table.
If you want BuddyPress to use something else for the profile URL, you can set the username in the user_nicename DB field and BuddyPress will use that for the user profile URL.
Keep in mind that this might break whatever custom configurations you might have on your install.
If you’d rather not mess with altering the data in the user DB columns, you can also filter 'bp_core_get_user_domain' and 'bp_core_set_uri_globals_member_slug'.
View this ticket for more info:
https://buddypress.trac.wordpress.org/ticket/6694