found the problem..
julianlam created this issue in psychobunny/nodebb-plugin-topic-badges
Fixed missing "topics" namespace in SocketAdmin
Then you will probably have to modify the sso plugin to reject or truncate usernames that are too long.
I'm not sure if NodeBB should reject things like creating an user by a plugin if the plugin doesn't adhere to admin settings, because there might be valid reasons for doing it. For example - you might have a username length limit, because you want to reserve longer usernames for bot users created by a plugin or something.