Merging Duplicate Contacts in Proofing HQ?

if you put in a ticket with Support, they can work with you to do this, as well as help you understand how this happens.

Hi there, you can work with WF to help clean this up on the back end, but here is info on what causes this to happen:
https://experienceleague.adobe.com/docs/workfront/using/administration-and-setup/manage-wf/configure-proofing/user-sync-proofing.html?lang=en 

From @brownpaperbag in a similar thread last year with this from support:

"Member accounts are created when the user is active with another company and is added to a different company's workflow. Guest accounts are created when the user does not exist at all in ProofHQ, and they are added to a workflow, or if the user does exist in ProofHQ, but is deactivated on the other account; if they are deactivated, the system does not add them as a member since they do not have an active login to another account, but instead will create them as a guest user. 

When a user with a matching email exists, in their own or in another proofing environment, Workfront creates an alias email address by adding the user’s account id as a suffix to their email. For example, username+accountid@domain.com. Users will still receive proof notifications in the event an alias email is created." - this last bit is reiterated in the link I posted above.

Please mark correct if this helped you in order to help others : )