So a person cannot have the same public key loaded into two different accounts?

[Daniel Wilches]

This question is in reference to Atlassian Documentation: Someone has already registered that SSH key

I'm getting this error message after trying to register my public key in one account, but I had the same public key also registered for another account.

So a person cannot have the same public key loaded into two different accounts? Why?

[Daniel Wester]

Correct. It's due to ssh (which git is using as the transfer protocol) uses it to identify you as well as to verify you. See https://www.quora.com/Why-cant-I-add-my-public-SSH-key-to-more-than-one-account-on-GitHub