Many accounts are anonymous, they have no display name. Right now it will display a wide hexadecimal string to identify them. Once upon a time it was using "Unknown" but people complained. Maybe "Anonymous (FFFFFFFF)" where FFFFFFFF is the first 8 chars of the hex hash. Or maybe go back to Uri Herrera solution and color code everybody, but this is hard on accessibility, which I care about.
This project is unfortunately no longer maintained. If a new maintainer wants to step up and take care, the project is archived here: https://invent.kde.org/network/ring-kde You can just clone it in your private namespace on invent.kde.org and if you have started to work on it and fixed/implemented something get it reviewed and the project unarchived. Sorry for the inconveniences.