Shared user names

We seem to have more than one (Possibly many?) forum users sharing the name "Firstname Lastname".

This was avoided in the old forum by automatically deploying a unique identifier. Not an ideal result but better than duplications.

If we assume people cannot be bothered to take time to put something unique into the appropriate fields of their login account, either during or after creation, would it at least be possible to force the identifier to be unique AND ensure that it cannot somehow be defaulted to "Firstname Lastname"?