If you are in a scoreboard team, your nametag will be displayed even if you have invisibility.

To reproduce:

1. Create a new world and open it to LAN
2. Run /scoreboard teams add newTeam
3. Run /scoreboard teams join newTeam @p
4. Join your game with another account
5. Drink a potion of invisibility
6. Observe how your nametag is visible to the other account (due to the default value 'always' for nametagVisibility)

To fix this, either make nametagVisibility not override invisibility or add another option for nametagVisibility which does not affect invisibility.