Per, the following link, merging accounts is not possible:
https://community.alteryx.com/t5/General-Discussions/Account-merge-migration/td-p/627381
Although an account can be associated to a new email.
According to the Alteryx Certification Policies (https://s3-us-west-1.amazonaws.com/ayx.policies/Alteryx+Certification+Policies.pdf):
"You will not circumvent, or attempt to circumvent, the Exam re-take policy by registering under a different name or email address or bypassing any
authorization or initialization systems".
It does not seem to indicate that simply having two accounts would preclude you from becoming certified, but rather that you cannot leverage both accounts to "loop-hole" the system if you fail, for instance.
I'll let someone else more qualified than I provide the official answer. That being said, based on my reading, I conclude that there is no issue with you picking one account as your main "community/certification account" and only use that for taking exams. If that account's access is going to change (due to changing employment or finished schooling) you can re-associate that main account to a new email so that all your badges/certifications aren't lost.
