Renaming the /home directory of the user fixed the original issue, thank you for that. But to give some clarification on my original question, here's the full scenario:
I have an Ubuntu 16.04 workstation bound to my AD domain using Centrify Express (we're in the process of standing up our Centrify Identity Management, long story, needed to start somewhere). I had a user experiencing some issues with his AD "profile" on said workstation but was unable to leverage the native Users & Accounts UI to remove/readd his account to the specific workstation (not AD as a whole). There starts my confusion: "why can't I remove the user object from the workstation through the native tool?" Fortunately, renaming the user's /home folder accomplished the desired result.
Outside of this, is there a way to remove all traces of a user's login to the workstation (ex, their /home directory and username in the login screen)? Basically, if I wanted to "clean up" a machine before sending it off to a new user (without going through the hassle of re-installing the OS) or needed to fix some interface problem with an existing user of the workstation.
Thanks again for your assistance thus far. I'm hoping that when we get the full suite of tools running it will be easier.
- Chad