Deleting your account was refused while you owned a team whose only other people were guests: the message asked you to transfer the team to another admin, and a guest cannot be an admin. Guests no longer count. When you delete your account, teams you own with no other members are archived, and every guest of those teams and of your Personal is removed and gets an email saying you deleted your account.
Fixed deleting your account when a team you own has only guests
Guests no longer stop you deleting your account. Each guest is removed and gets an email.