The user amWhy used to be an active participant on Math.SE. Here's their network profile.
I clicked on his/her per-site profiles, and each of them showed their new user name Namaste.
You may click on the screenshots to browse amWhy/Namaste's user profile.
How is this possible? One is allowed to have multiple names on the SE network?
Site user profiles have a link "Edit Profile & Settings" for changing user name. At the bottom of the HTML form, one may choose to update user profile for either one or all communities. After that, to apply such change to the SE network profile, one may click "Update profile info" in the network-wide page. It seems that amWhy has changed their user name and clicked "Save and copy changes to all public communities", so such change should be network-wide, and it's bizarre that the network profile user name has not been updated.
Your help is appreciated.