The panel is called the 'user accounts' panel, and the list is pretty clearly a list of accounts. The section headings say 'My Account' / 'Other Accounts'. Therefore, the tooltips on the +/- buttons should talk about accounts as well, not about users.

They should say

To create a new user account, click the * icon first

To delete the selected user account, click the * icon first

and when unlocked:

Create a user account

Delete the selected user account



Another thing we need to correct here is that the icon is now wrong. We use the open padlock in the 'Unlock' button, so the tooltip needs to show that icon, not the closed padlock.