What I did:
I add the person and I would like to delete it. But I cannot find a way how I should do it.
Things that might be helpful to know (Agenda version, OS and model, etc):
If you remove the person from your notes, I think it should remove the person in general, though it may only happen after a quit.
What does it mean to “remove a person in general” ?
It means that if you remove the last of the same person tags from your notes, it should also be removed from the auto-complete list (though that auto-complete list is no longer shown in version 6.0.1).
If the question is how to delete a person tag from the notes than you can either simply backspace into the person tag and delete it this way, or tap/click the person tag to show the popover, which also offers a delete option.
ah that was it. It sounded like maybe I was missing some person-related feature. thanks!