A former colleague at a place where I used to work added my personal MS account to a Teams community inside the organization. It split my Teams account in two, prompting me to choose which one I wanted to use every time I opened Teams.

One side was associated with the organisation, the other was still my personal account. My personal account became inaccessible and attempting to login would result in a referral loop and an error. The MS advice for the error code was to get the system admin to remove my account from the organisation, which wasn't possible because I don't work there anymore.