I was thinking it would be helpful to Abby if we came up with some standard wordings, and it still would be helpful, but a thought occurred to me. Why not have WikiTree disallow all requests to an active member to join their Trusted List? It would solve the problem of uninvited people trying to join your list. When they try, present a message saying "It's not the policy of WikiTree to allow requesting addition to the Trusted List of an active member. Make sure that you are applying for the correct profile. Otherwise, assuming you are a close relative, ask the member in person to add you." In other words, they can't go through WikiTree to do it, but they still can by talking directly with you (which means you have to know each other), and then you can manually add them if desired.
Then WikiTree can cancel all outstanding requests, with a reason like "It's a system maintenance thing". (You can blame almost anything on the computer or system maintenance!)
It still might be useful to suggest standard wordings here though, for situations like Debbie's. One might be something like (after rejecting it) "I feel responsible for that profile, and I only approve such requests after a personal note explaining why you want to be added." After you receive a note you like, then you can manually add them, or tell them to try again, and approve them this time.