Yes it is annoying b/c I don't know who's real & who's not, although I can tell most times now.
Unfortunately I'm still using a 3rd party hosted shopping cart that also runs my lists. Their code & features are sub par at best, so I doubt there's an option to self delete if they don't opt in. In fact I know there's not, as I've had to do it myself & have to do it soon, as I'm nearing my max.
I get notified of every signup whether it goes thru or not. Again, I doubt there's a feature that would ONLY let me know if they opted in.
This has been going on for months. I don't know if it's the same person or what's happening. I guess I could try to keep track of the IP addresses, but I just don't have time for that & they are probably using a proxy anyway.