How do I delete a person from family tree due to a mistake

When I mistakenly added a person, I "deleted" them by merging them with another person's profile. I included a detailed note describing why.

Yes, but only if you are the only person who has contributed at all to the 'mistaken' Family Tree profile - if so, you will be able to use the Delete Person option, to be found at the bottom right of the Details tab.