A security flaw was found in the way openldap and nss_ldap packages used to set up permissions for the configuration files for the LDAP service. An attacker could use this flaw to access potentially sensitive information, which should be otherwise protected.
Note the Debian bug report is referring to nss-ldapd which is a fork of nss_ldap and behaves quite differently. We do not ship nss-ldapd with any products.
In nss_ldap, /etc/ldap.conf typically needs to be accessible to non-privileged users for various programs to operate correctly. In the case of non-standard or exceptional configuration scenarios, users may change permissions when needed and implement required mechanisms to 'make things work', but there is currently no plan to change permissions on this file by default.