By default, Discourse does not support inputting Chinese usernames.
According to the official documentation, starting from Discourse version 2.3.0.beta9, Discourse has supported Unicode usernames, including Chinese usernames.
The official announcement is here: Unicode usernames and group names - announcements - Discourse Meta
You just need to configure your Discourse.
Setting Location
In the admin settings, search for the character unicode.
You will see an option called unicode usernames.
Just select this option.
If you are using an English version of Discourse.
Then this configuration option is located here.
A long time ago, some people discussed this, but that was when it was not officially supported.
You no longer need to install this plugin.