Currently
If you want to ban an identity user without deleting a comment, you can use the same console command. However, you will need to use the system name for the identity user in the console command. The easiest way to find the system name is to click the OpenID logo (OpenID logo icon) next to the user's name, which will bring you to that user's profile. Follow the "(more details...)" link at the bottom of that page to view the full profile. At the end of the full profile, you should see a section of the form:
Virtual Gifts
Received: 1 Send ext_1 a virtual gift
In this example, ext_1 is the system name for this identity user. You would then ban them by typing the following into the console:
ban_set ext_1
You will need to substitute the system name of the identity user you want to ban, instead of using "ext_1". (Note that you can use - or _ indifferently in the username.)
Proposed
If you want to ban an identity user without deleting a comment, you can use the same console command. However, you will need to use the system name for the identity user in the console command. The easiest way to find the system name is to click the OpenID logo (OpenID logo icon) next to the user's name, which will bring you to the user's profile. Mouse over any one of the three links at the top of the profile page (Memories, Virtual Gifts, or Userpics) and take note of the username which appears after the ?user= in the URL (which will appear in the form ext_#####).
ext_##### is the system name for this identity user. You would then ban them by typing the following into the console:
ban_set ext_#####
You will need to substitute the system name of the identity user you want to ban, instead of using "ext_#####". (Note that you can use - or _ indifferently in the username.)