"nick taken" is thrown incorrectly

When there's a lot of discussion, where you sign up multiple times, "nick taken" is thrown incorrectly. This means that people have to change their nick slightly, which means they get put in the first speak list incorrectly.

No files, tests, or entry points are identified in the issue. Reproduce the repeated sign-up flow, trace the nickname conflict behavior and its effect on the first-speak list, then add a regression test confirming valid sign-ups do not require changing the nickname.

Written by the indexing model from the issue text.