In practice, deleting is often not available (greyed out). This is because deleting a user who has logged time would also imply deleting his or her time entires, which in turn would undermine the internal consistency of your time administration.
So - if you want to remove a user from Yanomo, we advise you to either:
1. Deactivate this user. A deactivated user can no longer log in, and you will not be charged for deactivated users in your account. His or her time entries will remain available in reporting, and you can easily reactivate them when the need arises.
2. Manually delete all time entries associated with this user, after which you'll be able to (irreversibly) delete the user.