By clicking "Create an alias in your repository administration" the Alias is auto-filled with an invalid value

By clicking on the Author icon in the Commits page it shows the following popup (the Author icon is a question mark):

Unmapped user

This user is not recognised in Bitbucket.
Firstname Lastname <email_address>
Create an alias in your repository administration.

I've created an alias by clicking the link "Create an alias in your repository administration" and nothing was changes, still question mark and "Unmapped user" popup.

Then I suspected that the Alias field might be improperly filled automatically with an invalid value. I changed it from Firstname Lastname <email_address> to only email_address and the issue was gone.