thanks for posting. I've messaged the user in question regarding their accounts, but it's really their call whether they'd like to merge them or not. As detailed in this Meta post, there isn't a hard site policy on multiple accounts - you're free to do so provided you don't use them to upvote each other or otherwise manipulate the reputation system. If a user does choose to merge multiple accounts the recommended procedure is detailed here on the Meta help pages:
If you have two accounts that you would like to join together, please sign into either account, visit the contact form and select ‘I need to merge user profiles’. After you contact us, the Stack Exchange Team will reach out to verify that you own both accounts. If we can confirm your ownership, we will initiate a merge.