Migration Assistant and Bluesky user - BlueSkyTools/BlueSkyConnect GitHub Wiki

I found that when using Migration assistant to move even a single user to a new computer it seemed to also pull the invisible Bluesky user AND make it visible in System Preferences and at the login screen.

This Apple Technote describes how to make a user invisible again:

Hide a user account in macOS

sudo dscl . create /Users/hiddenuser IsHidden 1

So in our case it would be:

sudo dscl . create /Users/bluesky IsHidden 1